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Document And Entity Information - USD ($)	12 Months Ended
Document And Entity Information - USD ($)	Dec. 31, 2017	Feb. 26, 2018	Jun. 30, 2017
Document Information [Line Items]
Entity Registrant Name	ACELRX PHARMACEUTICALS INC
Entity Central Index Key	0001427925
Trading Symbol	acrx
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Common Stock, Shares Outstanding (in shares)		50,899,154
Entity Public Float			$ 75,622,608
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Amendment Flag	false

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 52,902	$ 80,310
Short-term investments	7,567
Accounts receivable, net	1,533	5,833
Inventories	956	2,154
Prepaid expenses and other current assets	455	756
Total current assets	63,413	89,053
Property and equipment, net	11,051	10,712
Restricted cash	178	178
Long-term tax receivable	703
Other assets	207	50
Total Assets	75,552	99,993
Liabilities and Stockholders’ Deficit
Accounts payable	1,424	1,558
Accrued liabilities	3,543	4,595
Long-term debt, current portion	7,727	2,912
Deferred revenue, current portion	362	362
Liability related to the sale of future royalties, current portion	604	764
Total current liabilities	13,660	10,191
Deferred rent, net of current portion	378	43
Long-term debt, net of current portion	11,369	18,637
Deferred revenue, net of current portion	3,463	3,824
Liability related to the sale of future royalties, net of current portion	82,984	72,223
Contingent put option liability	207	124
Warrant liability		288
Total liabilities	112,061	105,330
Commitments and Contingencies:
Common stock, $0.001 par value—100,000,000 shares authorized as of December 31, 2017 and December 31, 2016; 50,899,154 and 45,333,790 shares issued and outstanding as of December 31, 2017 and December 31, 2016	51	45
Additional paid-in capital	261,310	240,977
Accumulated deficit	(297,870)	(246,362)
Accumulated other comprehensive income		3
Total stockholders’ deficit	(36,509)	(5,337)
Total Liabilities and Stockholders’ Deficit	$ 75,552	$ 99,993

Consolidated Balance Sheets (Parentheticals) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	100,000,000	100,000,000
Common stock, issued (in shares)	50,899,154	45,333,790
Common stock, outstanding (in shares)	50,899,154	45,333,790

Consolidated Statements of Comprehensive Loss - USD ($)	12 Months Ended
Consolidated Statements of Comprehensive Loss - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Collaboration agreement	$ 7,143,000	$ 6,440,000	$ 14,857,000
Contract and other	852,000	10,917,000	4,406,000
Total revenue	7,995,000	17,357,000	19,263,000
Operating costs and expenses:
Cost of goods sold	10,659,000	12,315,000	1,770,000
Research and development	19,409,000	21,402,000	22,488,000
General and administrative	16,609,000	15,597,000	14,203,000
Restructuring costs			756,000
Total operating costs and expenses	46,677,000	49,314,000	39,217,000
Loss from operations	(38,682,000)	(31,957,000)	(19,954,000)
Other (expense) income:
Interest expense	(3,316,000)	(2,770,000)	(2,977,000)
Interest income and other income (expense), net	510,000	918,000	1,720,000
Non-cash interest expense on liability related to sale of future royalties	(10,721,000)	(9,382,000)	(2,428,000)
Total other (expense) income	(13,527,000)	(11,234,000)	(3,685,000)
Net loss before income taxes	(52,209,000)	(43,191,000)	(23,639,000)
Benefit (provision) for income taxes	701,000	34,000	(760,000)
Net loss	(51,508,000)	(43,157,000)	(24,399,000)
Other comprehensive income (loss):
Unrealized gains (losses) on available for sale securities	(3,000)	4,000	3,000
Comprehensive loss	$ (51,511,000)	$ (43,153,000)	$ (24,396,000)
Net loss per share of common stock, basic (in dollars per share)	$ (1.10)	$ (0.95)	$ (0.55)
Net loss per share of common stock, diluted (in dollars per share)	$ (1.10)	$ (0.95)	$ (0.60)
Shares used in computing net loss per share of common stock, basic (in shares)	46,883,535	45,313,118	44,300,099
Shares used in computing net loss per share of common stock, diluted –see Note 14 (in shares)	46,883,535	45,313,118	44,468,440

Consolidated Statements of Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2014	43,712,363
Balance at Dec. 31, 2014	$ 43	$ 225,423	$ (178,806)	$ (4)	$ 46,656
Stock-based compensation		5,010			5,010
Issuance of common stock upon exercise of stock options (in shares)	938,497
Issuance of common stock upon exercise of stock options	$ 1	2,769			$ 2,770
Issuance of common stock upon exercise of stock warrants (in shares)	527,101				527,101
Issuance of common stock upon exercise of stock warrants	$ 1	2,543			$ 2,544
Modification of warrants		100			100
Issuance of common stock upon ESPP purchase (in shares)	95,811
Issuance of common stock upon ESPP purchase		429			429
Change in unrealized gains and losses on investments				3	3
Net loss			(24,399)		(24,399)
Balance (in shares) at Dec. 31, 2015	45,273,772
Balance at Dec. 31, 2015	$ 45	236,274	(203,205)	(1)	33,113
Stock-based compensation		4,479			4,479
Modification of warrants		45			45
Issuance of common stock upon ESPP purchase (in shares)	60,018
Issuance of common stock upon ESPP purchase		179			179
Change in unrealized gains and losses on investments				4	4
Net loss			(43,157)		(43,157)
Balance (in shares) at Dec. 31, 2016	45,333,790
Balance at Dec. 31, 2016	$ 45	240,977	(246,362)	3	(5,337)
Stock-based compensation		4,294			$ 4,294
Issuance of common stock upon exercise of stock options (in shares)	69,372				69,372
Issuance of common stock upon exercise of stock options		105			$ 105
Issuance of common stock upon ESPP purchase (in shares)	94,893
Issuance of common stock upon ESPP purchase		246			246
Change in unrealized gains and losses on investments				(3)	(3)
Net loss			(51,508)		$ (51,508)
Net proceeds from issuance of common stock in connection with equity financings (in shares)	5,401,099				5,400,000
Net proceeds from issuance of common stock in connection with equity financings	$ 6	15,688			$ 15,694
Balance (in shares) at Dec. 31, 2017	50,899,154
Balance at Dec. 31, 2017	$ 51	$ 261,310	$ (297,870)		$ (36,509)

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (51,508)	$ (43,157)	$ (24,399)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash royalty revenue related to royalty monetization	(151)	(7)
Non-cash interest expense on liability related to royalty monetization	10,721	9,382	2,428
Depreciation and amortization	1,744	2,052	1,984
Non-cash interest expense related to debt financing	1,265	877	897
Stock-based compensation	4,294	4,479	5,010
Revaluation of put option and PIPE warrant liabilities	(205)	(767)	(2,136)
Loss on disposal and impairment of property and equipment	12		573
Inventory impairment charge	369
Other	(5)	17	114
Changes in operating assets and liabilities:
Accounts receivable	4,300	(2,547)	(3,286)
Inventories	920	(1,688)	(466)
Prepaid expenses and other assets	175	975	(783)
Restricted cash			72
Tax receivable	(703)
Accounts payable	309	(437)	(786)
Accrued liabilities	(1,301)	639	325
Deferred revenue	(361)	989	784
Deferred rent	360	(202)	(284)
Net cash used in operating activities	(29,765)	(29,395)	(19,953)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(2,405)	(3,720)	(1,456)
Purchase of investments	(7,565)	(996)	(7,266)
Proceeds from maturities of investments		6,525	16,925
Net cash (used in) provided by investing activities	(9,970)	1,809	8,203
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from sale of future royalties			61,184
Payment of long-term debt	(3,514)		(4,534)
Payment of debt modification transaction costs	(204)	(205)	(215)
Net proceeds from issuance of common stock in connection with equity financings	15,694
Net proceeds from issuance of common stock through equity plans	351	179	3,199
Net cash provided by (used in) financing activities	12,327	(26)	59,634
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(27,408)	(27,612)	47,884
CASH AND CASH EQUIVALENTS—Beginning of period	80,310	107,922	60,038
CASH AND CASH EQUIVALENTS—End of period	52,902	80,310	107,922
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for interest	2,043	1,893	2,115
Income taxes (refunded) paid	2	(55)	782
NONCASH INVESTING AND FINANCING ACTIVITIES:
Issuance of common stock upon cashless exercise of warrants			2,544
Modification of warrants for common stock		45	100
Purchases of property and equipment in Accounts payable	89	532	98
Purchases of property and equipment in Accrued liabilities	$ 133

Note 1 - Organization and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Basis of Presentation and Significant Accounting Policies [Text Block]

Organization and Summary of Significant Accounting Policies

The Company

AcelRx Pharmaceuticals, Inc., or the Company or AcelRx, was incorporated in Delaware on

July 13, 2005

as SuRx, Inc., and in

January 2006,

the Company changed its name to AcelRx Pharmaceuticals, Inc. The Company

’s operations are based in Redwood City, California.

AcelRx is a specialty pharmaceutical company focused on the development and commercialization of innovative therapies for the treatment of acute pain.

AcelRx’s lead product candidate, DSUVIA

™

(known as DZUVEO outside of the United States), and its follow-on product candidate, ZALVISO

, each utilize sublingual sufentanil, delivered via a non-invasive route of sublingual administration. Subject to obtaining regulatory approvals, AcelRx anticipates developing a distribution capability and commercial organization in the United States to market and sell DSUVIA in the United States by itself, and potentially, in certain European Economic Area, or EEA, countries with strategic partners. In geographies where AcelRx decides

not

to commercialize products by itself, the Company

may

seek to out-license commercialization rights. AcelRx intends to seek regulatory approval for ZALVISO in the United States and, if successful, potentially promote ZALVISO either by itself or with strategic partners.

DSUVIA

DSUVIA, is a

mcg sufentanil sublingual tablet in a single-dose applicator intended for the treatment of moderate-to-severe acute pain administered by a healthcare professional. DSUVIA

was initially developed at the request of the U.S. Department of Defense as a replacement for injections of morphine on the battlefield. In addition to the military application, AcelRx is developing DSUVIA for the treatment of patients suffering from moderate-to-severe acute pain in multiple settings, such as emergency room patients; patients who are recovering from short-stay or ambulatory surgery and do

not

require more long-term analgesia; post-operative patients who are transitioning from the operating room to the recovery floor; certain types of office-based or hospital-based procedures; patients being treated and transported by paramedics. The Company completed the Phase

clinical program for DSUVIA and in

February 2017

a New Drug Application, or NDA, was accepted for filing by the U.S. Food and Drug Administration, or FDA, for DSUVIA for the treatment of moderate-to-severe acute pain to be administered by a healthcare professional in medically supervised settings. On

October 12, 2017,

the Company received a Complete Response Letter, or CRL, from the FDA regarding its NDA for DSUVIA which states the FDA determined it cannot approve the NDA in its present form and provides recommendations for resubmission. The CRL contained

two

primary recommendations. First, while the safety database was suitable in number of patients, the collection of additional data was requested on at least

patients to assess the safety of DSUVIA dosed at the maximum amount described in the proposed labelling. Second, to ensure proper administration of the tablet with the single-dose applicator, the FDA recommended certain changes to the Directions for Use, or DFU, to address use-related errors, including dropped tablets, which changes would need to be validated through a Human Factors, or HF, study. The Company had a

Type A post-action

meeting with the FDA on

January 26, 2018

to discuss the topics covered in the CRL and to clarify the path to move towards resubmission of the DSUVIA NDA, which the Company expects to resubmit in the

second

quarter of

2018,

following the completion of an HF study to validate the revised DFU. In

March 2017,

the European Medicines Agency, or EMA, notified the Company that the DZUVEO (sufentanil sublingual tablet,

mcg) Marketing Authorisation Application, or MAA, has passed validation, and that the scientific review of the MAA is underway. The MAA for DZUVEO (formerly known as ARX-

) was filed for the treatment of patients with moderate-to-severe acute pain in a medically supervised setting. AcelRx expects an opinion on the MAA from the Committee for Medicinal Products for Human Use, or CHMP, in the

first

half of

2018

ZALVISO

ZALVISO delivers

mcg sufentanil sublingually through a non-invasive delivery route via a pre-programmed, patient-controlled analgesia, or PCA, system. ZALVISO is approved in the EEA, Norway, Iceland and

Liechtenstein and is in late-stage development in the U.S. The Company had initially submitted to the FDA an NDA seeking approval for ZALVISO in

September 2013

but received a CRL on

July 25, 2014.

Subsequently, the FDA requested an additional clinical study,

IAP312,

designed to evaluate the effectiveness of changes made to the functionality and usability of the ZALVISO device and to take into account comments from the FDA on the study protocol. In the

IAP312

study, for which top-line results were announced in

August 2017,

ZALVISO met safety, satisfaction and device usability expectations. These results will supplement the

three

Phase

trials already completed in the ZALVISO NDA resubmission. The Company plans to resubmit the NDA for ZALVISO in the

second

half of

2018.

December 16, 2013,

AcelRx and Grü

nenthal GmbH, or Grünenthal, entered into a Collaboration and License Agreement, or the License Agreement, which was amended effective

July 17, 2015

and

September 20, 2016,

or the Amended License Agreement, which grants Grünenthal rights to commercialize ZALVISO PCA system, or the Product, in the countries of the EU, Switzerland, Liechtenstein, Iceland, Norway and Australia (collectively, the Territory) for human use in pain treatment within, or dispensed by, hospitals, hospices, nursing homes and other medically supervised settings, or the Field. In

September 2015,

the European Commission, or EC, approved the Marketing Authorization Application, or MAA, previously submitted to the European Medicines Agency, or EMA, for ZALVISO for the management of acute moderate-to-severe post-operative pain in adult patients. The approval allows Grünenthal to market ZALVISO in the

EU member states as well as for the EEA, Norway, Iceland and Liechtenstein, or EEA. Also on

December 16, 2013,

AcelRx and Grünenthal, entered into a related Manufacture and Supply Agreement, or the MSA, and together with the License Agreement, the Agreements. Under the MSA, the Company will exclusively manufacture and supply the Product to Grünenthal for the Field in the Territory. On

July 22, 2015,

the Company entered into an amendment to the MSA, or the MSA Amendment, and together with the MSA, the Amended MSA, between the Company and Grünenthal, effective as of

July 17, 2015,

and together with the Amended License Agreement, the Amended Agreements.

Grü

nenthal has begun its commercial launch of ZALVISO in the European Union. Royalty revenues and non-cash royalty revenues from the commercial sales of ZALVISO in the EU are expected to be minimal for

2018

The Company has incurred recurring operating losses and negative cash flows from operating activities since inception. Although ZALVISO has been approved for sale in the EU, the Company sold the majority of the royalty rights and certain commercial sales milestones it is entitled to receive under the Amended License Agreement with Grünenthal to PDL BioPharma, Inc., or PDL. As a result, the Company expects to continue to incur operating losses and negative cash flows.

When we refer to "we," "our," "us," the "Company" or "AcelRx" in this document, we mean the current Delaware corporation, or AcelRx Pharmaceuticals, Inc., and its predecessor, as well as its consolidated subsidiary.

Basis of Presentation

The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and the accompanying notes. Actual results could differ from those estimates.

Reclassifications

Certain prior year amounts in the Consolidated Financial Statements have been reclassified to conform to the current year's presentation.

In particular, the amounts reported in the Consolidated Statements of Cash Flows as “Amortization of premium/discount on investments, net” have been reclassified to “Other” for the years ended

December 31, 2016

and

December 31, 2015.

Principles of Consolidation

The Consolidated Financial Statements include the accounts of the Company and its wholly

owned subsidiary, ARPI LLC, which was formed in

September 2015

for the sole purpose of facilitating the monetization transaction with PDL of the expected royalty stream and milestone payments due from the sales of ZALVISO in the European Union by its commercial partner,

Grünenthal, pursuant to the Amended License Agreement, or the Royalty Monetization. All intercompany accounts and transactions have been eliminated in consolidation. Refer to Note

“Liability Related to Sale of Future Royalties” for additional information.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the Consolidated Financial Statements and accompanying notes. Management evaluates its estimates on an ongoing basis including critical accounting policies. Estimates are based on historical experience and on various other market-specific and other relevant assumptions that the Company believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are

not

readily apparent from other sources. Actual results could differ from those estimates.

Cash, Cash Equivalents and Marketable Securities

The Company considers all highly liquid investments with an original maturity (at date of purchase) of

three

months or less to be cash equivalents. Cash and cash equivalents consist of cash on deposit with banks.

All marketable securities are classified as available-for-sale and consist of U.S. government sponsored enterprise debt securities. These securities are carried at estimated fair value, which is based on quoted market prices or observable market inputs of almost identical assets, with unrealized gains and losses included in accumulated other comprehensive income (loss). The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income or expense. The cost of securities sold is based on specific identification. The Company

’s investments are subject to a periodic impairment review for other-than-temporary declines in fair value. The Company’s review includes the consideration of the cause of the impairment including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in the market value. When the Company determines that the decline in fair value of an investment is below its accounting basis and this decline is other-than-temporary, it reduces the carrying value of the security it holds and records a loss in the amount of such decline.

Fair Value of Financial Instruments

The Company measures and reports its cash equivalents, investments and financial liabilities at fair value. Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy defines a

three

-level valuation hierarchy for disclosure of fair value measurements as follows:

Level I

—Unadjusted quoted prices in active markets for identical assets or liabilities;

Level II

—Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are

not

active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and

Level III

—Unobservable inputs that are supported by little or

market activity for the related assets or liabilities.

The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.

Segment Information

The Company operates in a single segment, the development and commercialization of product candidates for the treatment of pain. The Company

’s contract revenue relates to sales in the United States. The Company’s collaboration revenue relates to the Amended License Agreement with Grünenthal to commercialize ZALVISO in the countries of the European Union, Switzerland, Liechtenstein, Iceland, Norway and Australia.

Concentration of Risk

The Company invests cash that is currently

not

being used for operational purposes in accordance with its investment policy in debt securities of U.S. government sponsored agencies and overnight deposits. The Company is exposed to credit risk in the event of default by the institutions holding the cash equivalents and available-for-sale securities to the extent recorded on the Consolidated Balance Sheet

The Company relies on a single

third

-party supplier for the supply of sufentanil, the active pharmaceutical ingredient in

ZALVISO, and various sole-source

third

-party contract manufacturer organizations to manufacture the ZALVISO drug cartridge and device components, including the controller, the dispenser kit and the accessories.

To date, the Company has had only

two

customers. These

two

customers account for

100%

of the revenues for the years ended

December 31,

2017,

2016

and

2015.

One of these customers accounted for

79%

of the accounts receivable balance as of

December 31, 2017,

while the other customer accounted for

71%

and

84%

of the accounts receivable balance as of

December 31, 2016

and

2015,

respectively.

The Company has

not

experienced any losses with respect to the collection of its

accounts receivable and believes that the entire accounts receivable balance as of

December 31, 2017

is collectible.

Accounts Receivable, Net

The Company has receivables from its collaboration partner and the U.S. Department of Defense, or DoD. To date, the Company has

not

had a bad debt allowance because of the limited number of financially sound customers who have historically paid their balances timely. The need for a bad debt allowance is evaluated each reporting period based on the Company

’s assessment of the credit worthiness of its customers or any other potential circumstances that could result in bad debt.

Inventories

Inventories are valued at the lower of cost

and net realizable value. Cost is determined using the

first

-in,

first

-out method for all inventories. Inventory includes the cost of the active pharmaceutical ingredients, or API, raw materials and

third

-party contract manufacturing and packaging services. Indirect overhead costs associated with production and distribution are allocated to the appropriate cost pool and then absorbed into inventory based on the units produced or distributed, assuming normal capacity, in the applicable period.

Indirect overhead costs in excess of normal capacity are recorded as period costs in the period incurred.

The Company's policy is to write down inventory that has become obsolete, inventory that has a cost basis in excess of its expected net realizable value and inventory in excess of expected requirements. The Company periodically evaluates the carrying value of inventory on hand for potential excess amount over demand using the same lower of cost or market approach as that used to value the inventory.

During the year ended

December 31, 2017,

the Company recorded an inventory impairment charge of

$0.4

million, primarily for ZALVISO raw materials inventory on hand, plus related purchase commitments.

Because selling prices to Grünenthal

are set to recover only direct costs with minimal mark up, all inventories are carried at net realizable value.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets, generally

three

five

years. Leasehold improvements are amortized over the shorter of the estimated useful life of the improvements or the remaining lease term.

Expenditures for repairs and maintenance, which do

not

extend the useful life of the property and equipment, are expensed as incurred. Upon retirement, the asset cost and related accumulated depreciation are relieved from the accompanying Consolidated Balance Sheets. Gains and losses associated with dispositions are reflected as a component of Other (expense) income in the accompanying Consolidated Statements of Comprehensive Loss.

Impairment of Long-Lived Assets

The Company periodically assesses the impairment of long-lived assets and, if indicators of asset impairment exist, the Company assesses the recoverability of the affected long-lived assets by determining whether the carrying value of such assets can be recovered through an analysis of the undiscounted future expected operating cash flows. If impairment is indicated, the Company records the amount of such impairment for the excess of the carrying value of the asset over its estimated fair value. For example, purchased equipment and manufacturing-related facility improvements the Company has made at Patheon

’s facility in Ohio, are utilized for continued research and development, commercial manufacturing of ZALVISO for Grünenthal and potential commercialization of its other product candidates. If the Company does

not

receive regulatory approval for its other product candidates, the Company

may

determine that it is

longer probable that the Company will realize the future economic benefit associated with the costs of these assets through future manufacturing activities, and if so, the Company would record an impairment charge associated with these assets. As of

September 30, 2015,

the Company remeasured on a non-recurring basis a portion of its leasehold improvements in its corporate offices using Level III valuation techniques. The write down to fair value of these long-lived assets resulted in an impairment charge of

$0.5

million in the year ended

December 31, 2015,

which was recorded in interest income and other income (expense), net in the Consolidated Statements of Comprehensive Loss. As of

December

31,

2017,

the Company has

not

written down any additional long-lived assets as a result of impairment.

Restricted Cash

Under the Company

’s facility lease and corporate credit card agreements, the Company is required to maintain letters of credit as security for performance under these agreements. The letters of credit are secured by certificates of deposit in amounts equal to the letters of credit, which are classified as restricted cash on the Consolidated Balance Sheets.

Debt Issuance Costs

Debt issuance costs, which are included in long-term debt, net of current portion, are amortized as interest expense over the contractual terms of the related credit facilities.

Contingent put option

The contingent put option associated with the Company

’s loan and security agreement with Hercules Technology II, L.P. and Hercules Technology Growth Capital, Inc., collectively referred to as the Lenders, is recorded as a liability. Changes in the fair value of the contingent put option are recognized as interest income and other income (expense), net in the Consolidated Statements of Comprehensive Loss. For additional information regarding the contingent put option, see Note

“Long-Term Debt”.

Warrants

Warrants issued in connection with the Company

’s Private Placement, completed in

June 2012,

are recorded as liabilities as they have the potential for cash settlement upon the occurrence of certain transactions (as defined in the warrant; see Note

“Warrants”). Changes in the fair value of the warrants are recognized as interest income and other income (expense), net in the Consolidated Statements of Comprehensive Loss.

Revenue Recognition

The Company recognizes revenue when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; the fee is fixed or determinable; and collectability is reasonably assured.

Collaboration Revenue

Collaboration revenue, which is earned under license agreements with

third

parties,

may

include nonrefundable license fees, cost reimbursements, research and development services, commercial manufacturing services, contingent development and commercial milestones and royalties.

AcelRx accounts for multiple-element arrangements in accordance with ASC Topic

605

25,

Revenue Recognition—Multiple-Element Arrangements

, or ASC

605

25.

The Company evaluates if the deliverables in the arrangement represent separate units of accounting. In determining the units of accounting, AcelRx evaluates certain criteria, including whether the deliverables have value to our customers on a stand-alone basis. Factors considered in this determination include whether the deliverable is proprietary to the Company, whether the customer can use the license or other deliverables for their intended purpose without the receipt of the remaining elements, whether the value of the deliverable is dependent on the undelivered items, and whether there are other vendors that can provide the undelivered items. Deliverables that meet these criteria are considered a separate unit of accounting. Deliverables that do

not

meet these criteria are combined and accounted for as a single unit of accounting.

For revenue agreements with multiple-element arrangements, such as the collaboration and license agreement with Grünenthal, the Company allocates revenue to each non-contingent element based on the relative selling price of each element. When applying the relative selling price method, the Company determines the selling price for each deliverable using

vendor-specific objective evidence, or

VSOE, of selling price or

third

-party evidence, or

TPE, of selling price. If neither exists the Company uses best estimated selling price, or

BESP, for that deliverable. Revenue allocated is then recognized when the

four

basic revenue recognition criteria are met for each element.

VSOE is based on the price charged when the element is sold separately and is the price actually charged for that deliverable. Establishing VSOE

may

not

be possible for the elements of a license arrangement because each arrangement is unique, an arrangement typically consists of multiple elements and AcelRx has limited history of entering into license arrangements. When VSOE cannot be established, AcelRx attempts to establish the selling price of the elements of a license arrangement based on TPE. TPE is determined based on a competitor

’s price for similar deliverables when sold separately. AcelRx

may

not

be able to determine TPE for license arrangements, as they contain a significant level of differentiation such that the comparable pricing of a competitor’s license arrangement with similar functionality cannot be obtained, and AcelRx is therefore unable to reliably determine what a similar competitor’s license arrangement’s selling price would be on a standalone basis.

When AcelRx is unable to establish the selling price of an element using VSOE or TPE, BESP is utilized in the allocation of the elements of the arrangement. The objective of the BESP is to determine the price at which AcelRx would transact a sale if the element of the license arrangement were sold on a standalone basis.

The process for determining BESPs involves management

’s judgment. AcelRx’ process considers multiple factors such as discounted cash flows, estimated direct expenses and other costs and available data, which

may

vary over time, depending upon the circumstances, and relate to each deliverable. If the estimated obligation period of

one

or more deliverables should change, the future amortization of the revenue would also change.

AcelRx recognizes a contingent milestone payment as revenue in its entirety upon our achievement of the milestone. A milestone is substantive if the consideration earned from the achievement of the milestone (i)

is consistent with performance required to achieve the milestone or the increase in value to the delivered item, (ii) relates solely to past performance and (iii) is reasonable relative to all of the other deliverables and payments within the arrangement.

Contract and Other Revenue

May 2015,

the Company entered into the DoD Contract with the USAMRMC to support the development of

DSUVIA. The DoD Contract provides for the reimbursement of qualified expenses for development, manufacturing, regulatory and clinical costs outlined in the contract in order to submit an NDA to the FDA, including reimbursement for certain personnel and overhead expenses, as defined under the terms of the contract. Revenue under the contract is recognized when the related qualified expenses are incurred. The Company is entitled to reimbursement of overhead costs associated with the study costs incurred under the DoD Contract. The Company estimates this overhead rate by utilizing forecasted expenditures. Final reimbursable overhead expenses are dependent on direct labor and direct reimbursable expenses throughout the life of the DoD Contract, and as a result,

may

increase or decrease based on actual expenses incurred.

Cost of Goods Sold

Under the Amended Agreements with Grünenthal, the Company will sell

ZALVISO to Grünenthal at direct cost with minimal markup and will recognize indirect costs as period costs where they are in excess of normal capacity and

not

realizable on a lower of cost or market basis. Cost of goods sold for ZALVISO shipped to Grünenthal includes the inventory costs of API,

third

-party contract manufacturing costs, packaging and distribution costs, shipping, handling and storage costs, depreciation and costs of the employees involved with production.

Research and Development Expenses

Research and development costs are charged to expense when incurred. Research and development expenses include salaries, employee benefits, including stock-based compensation, consultant fees, laboratory supplies, costs associated with clinical trials and manufacturing, including contract research organization fees, other professional services and allocations of corporate costs. The Company reviews and accrues clinical trial expenses based on work performed, which relies on estimates of total costs incurred based on patient enrollment, completion of patient studies and other events.

Stock-Based Compensation

Compensation expense for all share-based payment awards made to employees and directors, including employee stock options

and restricted stock units related to the

2011

Equity Incentive Plan, or

2011

EIP, and employee share purchases related to the

2011

Employee Stock Purchase Plan, or ESPP, is based on estimated fair values at grant date. The Company determines the grant date fair value of the awards using the Black-Scholes option-pricing model and generally recognizes the fair value as stock-based compensation expense on a straight-line basis over the vesting period of the respective awards.

The Black-Scholes option pricing model requires inputs such as expected term, expected volatility and risk-free interest rate. These inputs are subjective and generally require significant analysis and judgment to develop. Estimates of expected life

during the years ended

December 31, 2016

and

2015,

were primarily determined using the simplified method in accordance with guidance provided by the SEC. Such method was utilized as the Company did

not

believe its historical option exercise experience, which was limited, provided a reasonable basis upon which to estimate expected term. During this period, volatility was derived from historical volatilities of several public companies within AcelRx’s industry that were deemed to be comparable to AcelRx’s business because AcelRx had insufficient history on the volatility of its common stock relative to the expected life assumptions used by the Company. During the year ended

December 31, 2017,

the Company determined that its historical data provided a reasonable basis for estimating future behavior in regards to expected term and volatility, and as a result, began using its historical option exercise experience and the volatility of its common stock as the basis for these assumptions. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant commensurate with the expected life assumption. Further, during the years ended

December 31, 2016

and

2015,

the Company estimated forfeitures at the time of grant and revised those estimates in subsequent periods if actual forfeitures differed from those estimates. Effective

January 1, 2017,

the Company adopted ASU

2016

and elected to recognize forfeitures when they occur using a modified retrospective approach, which did

not

have a material impact on its Consolidated Financial Statements.

Restructuring Costs

The Company's restructuring costs consist of employee termination benefit costs. Liabilities for costs associated with the cost reduction plan are recognized when the liability is incurred and are measured at fair value. One-time termination benefits are expensed at the date the entity notifies the employee, unless the employee must provide future service, in which case the benefits are expensed ratably over the future service period.

Non-Cash Interest Expense on Liability Related to Sale of Future Royalties

September 2015,

the Company

sold certain royalty and milestone payment rights from the sales of ZALVISO in the European Union by its commercial partner, Grünenthal, pursuant to the Collaboration and License Agreement, dated as of

December 16, 2013,

as amended, to PDL for an upfront cash purchase price of

$65.0

million, referred to as the Royalty Monetization. The Company continues to have significant continuing involvement in the Royalty Monetization primarily due to an obligation to act as the intermediary for the supply of ZALVISO to

Grünenthal. Under the relevant accounting guidance, because of the Company’s significant continuing involvement, the Royalty Monetization has been accounted for as a liability that will be amortized using the interest method over the life of the arrangement. In order to determine the amortization of the liability, the Company is required to estimate the total amount of future royalty

and milestone payments to be received by PDL and payments the Company is required to make to PDL, up to a capped amount of

$195.0

million, over the life of the arrangement. The sum of the capped amount of

$195.0

million, less the

$61.2

million of net proceeds the Company received will be recorded as interest expense over the life of the liability. Consequently, the Company imputes interest on the unamortized portion of the liability and record interest expense using an estimated interest rate for an arms-length debt transaction. The Company’s estimate of the interest rate under the arrangement is based on the amount of royalty and milestone payments expected to be received by PDL over the life of the arrangement. The Company’s estimate of this total interest expense resulted in an effective annual interest rate of approximately

14%.

The Company will periodically assess the expected royalty and milestone payments using a combination of historical results, internal projections and forecasts from external sources. To the extent such payments are greater or less than its initial estimates or the timing of such payments is materially different than its original estimates, the Company will prospectively adjust the amortization of the liability and the interest rate.

The Company

will record non-cash royalty revenues and non-cash interest expense within its Consolidated Statements of Comprehensive Loss over the term of the PDL agreement.

Comprehensive Loss

Comprehensive loss is comprised of net loss and other comprehensive income (loss) and is disclosed in the Consolidated Statements of Comprehensive Loss. For the Company, other comprehensive income (loss) consists of changes in unrealized gains and losses on the Company

’s investments.

Income Taxes

Deferred tax assets and liabilities are measured based on differences between the financial reporting and tax basis of assets and liabilities using enacted rates and laws that are expected to be in effect when the differences are expected to reverse. The Company records a valuation allowance for the full amount of deferred assets, which would otherwise be recorded for tax benefits relating to operating loss and tax credit carryforwards, as realization of such deferred tax assets cannot be determined to be more likely than

not.

Net Loss per Share of Common Stock

The Company

’s basic net loss per share of common stock is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding for the period. The diluted net loss per share of common stock is computed by giving effect to all potential common stock equivalents outstanding for the period determined using the treasury stock method. For purposes of this calculation, convertible preferred stock, options to purchase common stock, restricted stock subject to repurchase, warrants to purchase convertible preferred stock and warrants to purchase common stock were considered to be common stock equivalents. In periods with a reported net loss, such common stock equivalents are excluded from the calculation of diluted net loss per share of common stock if their effect is antidilutive. For additional information regarding the net loss per share, see Note

“Net Loss per Share of Common Stock”.

Recently

Adopted Accounting Pronouncement

March 2016,

the FASB issued ASU

No.

2016

09,

Compensation - Stock Compensation (Topic

718

)

, which is part of the FASB's Simplification Initiative. The updated guidance simplifies the accounting for share-based payment transactions. The amended guidance is effective for fiscal years, and interim periods within those years, beginning after

December 15, 2016,

with early adoption permitted. Under this guidance, on a prospective basis, companies will

longer record excess tax benefits and certain tax deficiencies as additional paid-in capital. Instead, they will record all excess tax benefits and tax deficiencies as income tax expense or benefit in the income statement. In addition, the guidance eliminates the requirement that excess tax benefits be realized before companies can recognize them. The ASU requires a cumulative-effect adjustment for previously unrecognized excess tax benefits in opening retained earnings in the annual period of adoption. Effective

January 1, 2017,

the Company adopted this updated guidance. Upon adoption, the Company recognized additional excess tax benefits as a deferred tax asset with a corresponding increase to our deferred tax asset valuation allowance, which did

not

result in a net impact to retained earnings, and elected to recognize forfeitures when they occur using a modified retrospective approach, which did

not

have a material impact on its Consolidated Financial Statements.

July 2015,

the FASB issued ASU

No.

2015

11,

Inventory (Topic

330

) Related to Simplifying the Measurement of Inventory,

which applies to all inventory measured using

first

-in,

first

-out (“FIFO”) or average cost. Inventory within the scope of the new guidance should be measured at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. ASU

No.

2015

was adopted by the Company beginning in fiscal

2017,

and did

not

have a material impact on its Consolidated Financial Statements.

Recently Issued

Accounting Pronouncements

May 2017,

the FASB issued ASU

2017

09,

Compensation - Stock Compensation (Topic

718

Scope of Modification Accounting

, to clarify which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting under ASC

718.

Under the new guidance, an entity will

not

apply modification accounting to a share-based payment award if all of the following remain unchanged immediately before and after the change of terms and conditions:

•

The award’s fair value (or calculated value or intrinsic value, if those measurement methods are used),

•

The award’s vesting conditions, and

•

The award’s classification as an equity or liability instrument.

ASU

2017

is effective for annual periods, and interim periods within those annual periods, beginning after

December 15, 2017

for all entities. Early adoption is permitted, including adoption in any interim period for which financial statements have

not

yet been issued or made available for issuance. The ASU will be applied prospectively to awards modified on or after the adoption date. The Company does

not

expect the adoption of ASU

2017

to have a material effect on its results of operations, financial condition or cash flows.

November 2016,

the FASB issued ASU

No.

2016

18,

Statement of Cash Flows (Topic

230

): Restricted Cash

. ASU

No.

2016

is intended to reduce diversity in practice in the classification and presentation of changes in restricted cash on the condensed consolidated statement of cash flows. The ASU requires that the condensed consolidated statement of cash flows explain the change in total cash and equivalents and amounts generally described as restricted cash or restricted cash equivalents when reconciling the beginning-of-period and end-of-period total amounts. The ASU also requires a reconciliation between the total of cash and equivalents and restricted cash presented on the condensed consolidated statement of cash flows and the cash and equivalents balance presented on the condensed consolidated balance sheet. ASU

2016

is effective retrospectively on

January 1, 2018,

with early adoption permitted. The Company does

not

expect the adoption of ASU

2016

to have a material effect on its results of operations, financial condition or cash flows.

August 2016,

the

FASB issued ASU

No.

2016

15,

Statement of Cash Flows (Topic

230

): Classification of Certain Cash Receipts and Cash Payments,

addressing

eight

specific cash flow issues in an effort to reduce diversity in practice. The amended guidance is effective for fiscal years beginning after

December 15, 2017,

and for interim periods within those years. Early adoption is permitted. The Company does

not

expect the amended guidance to have a material impact on its Consolidated Statements of Cash Flows.

February 2016,

the FASB issued ASU

No.

2016

02,

Leases (Topic

842

)

, which establishes a new lease accounting model for lessees. The updated guidance requires an entity to recognize assets and liabilities arising from a lease for both financing and operating leases, along with additional qualitative and quantitative disclosures. The amended guidance is effective for fiscal years, and interim periods within those years, beginning after

December 15, 2018,

with early adoption permitted. The Company has

not

yet selected a transition date, and is currently evaluating the impact of the adoption of this standard on its Consolidated Financial Statements.

May 2014,

the FASB issued ASU

No.

2014

09,

Revenue from Contracts with Customers

, to provide guidance on revenue recognition. ASU

No.

2014

requires a company to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under today’s guidance. These

may

include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. In

August 2015,

the FASB issued ASU

No.

2015

14,

Revenue from Contracts with Customers (Topic

606

): Deferral of the Effective Date

, which provided for the adoption of the new standard for fiscal years beginning after

December 15, 2017.

Accordingly, ASU

No.

2014

is effective for the Company in the

first

quarter of

2018.

Early adoption up to the

first

quarter of

2017

was permitted. Upon adoption, ASU

No.

2014

can be applied retrospectively to all periods presented or only to the most current period presented with the cumulative effect of changes reflected in the opening balance of retained earnings in the most current period presented. The FASB has also issued the following standards which clarify ASU

No.

2014

and have the same effective date as the original standard:

●

ASU

No.

2016

08,

Revenue from Contracts with Customers (Topic

606

): Principal versus Agent Considerations (Reporting Revenue Gross versus Net)

;

●

ASU

No.

2016

10,

Identifying Performance Obligations and Licensing (Topic

606

);

●

ASU

No.

2016

11,

Revenue Recognition (Topic

605

) and Derivatives and Hedging (Topic

815

): Rescission of SEC Guidance Because of Accounting Standards Updates

2014

and

2014

Pursuant to Staff Announcements at the

March 3, 2016

EITF Meeting;

●

ASU

No.

2016

12,

Revenue from Contracts with Customers (Topic

606

): Narrow-Scope Improvements and Practical Expedients; and

●

ASU

No.

2016

20,

Revenue from Contracts with Customers (Topic

606

): Technical Corrections and Improvements

The Company

adopted the new standard effective

January 1, 2018

under the modified retrospective transition method. The analysis identifying areas impacted by the new guidance is complete. The Company has completed its evaluation of its contract with the U.S. Department of Defense and the Amended Agreements with its collaboration partner Grünenthal, and the Company has determined that the impact of adoption of the new standard to its financial statements will

not

be material. In addition, there is

change to the units of accounting previously identified under legacy GAAP which are now considered performance obligations under the new guidance.

Note 2 - Investments and Fair Value Measurement

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Investments and Fair Value Measurement Disclosure [Text Block]

Investments and Fair Value Measurement

Investments

The Company classifies its marketable securities as available-for-sale and records its investments at fair value. Available-for-sale securities are carried at estimated fair value based on quoted market prices or observable market inputs of almost identical assets, with the unrealized holding gains and losses included in accumulated other comprehensive income. Marketable securities which have maturities beyond

one

year as of the end of the reporting period are classified as

non-current.

The table below summarizes the Company

’s cash, cash equivalents and investments (in thousands):

	As of December 31 , 201 7
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Cash and cash equivalents:
Cash	$	29,765	$	—	$	—	$	29,765
U.S. government agency securities		23,137		—		—		23,137
Total cash and cash equivalents		52,902		—		—		52,902

Marketable securities :
U.S. government agency securities	$	7,567	$	—	$	—	$	7,567
Total marketable securities		7,567		—		—		7,567

Total cash, cash equivalents and investments	$	60,469	$	—	$	—	$	60,469

	As of December 31 , 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Cash and cash equivalents:
Cash	$	49,833	$	—	$	—	$	49,833
U.S. government agency securities		30,474		3		—		30,477
Total cash and cash equivalents		80,307		3		—		80,310
Total cash, cash equivalents and investments	$	80,307	$	3	$	—	$	80,310

None

of the available-for-sale securities held by the Company had material unrealized losses and there were

realized losses for the years ended

December

31,

2017

and

2016.

There were

other-than-temporary impairments for these securities as of

December

31,

2017

2016.

gross realized gains or losses were recognized on the available-for-sale securities and, accordingly, there were

amounts reclassified out of accumulated other comprehensive income to earnings during the years ended

December 31, 2017

and

2016.

As of

December

31,

2017

and

2016,

the contractual maturity of all investments held was less than

one

year.

Fair Value Measurement

The Company

’s financial instruments consist of Level II assets and Level III liabilities. For Level II instruments, the Company estimates fair value by utilizing

third

party pricing services in developing fair value measurements where fair value is based on valuation methodologies such as models using observable market inputs, including benchmark yields, reported trades, broker/dealer quotes, bids, offers and other reference data. Such Level II instruments typically include U.S. treasury and U.S. government agency obligations. As of

December

31,

2017

and

December

31,

2016,

the Company held, in addition to Level II assets, a contingent put option liability associated with the Company’s Amended and Restated Loan and Security Agreement, or the Original Loan Agreement, with Hercules Technology II, L.P. and Hercules Capital, Inc., formerly known as Hercules Technology Growth Capital, Inc., collectively referred to as the Lenders, which amended and restated the Loan and Security Agreement dated as of

June 29, 2011,

which was classified as a Level III liability. On

March 2, 2017,

the Company entered into an Amended and Restated Loan and Security Agreement, or the Amended Loan Agreement with Hercules Capital Funding Trust

2014

and Hercules Technology II, L.P., together, Hercules. The Amended Loan Agreement amends and restates the Original Loan Agreement. See Note

“Long-Term Debt” for further description. The Company’s estimate of fair value of the contingent put option liability was determined by using a risk-neutral valuation model, wherein the fair value of the underlying debt facility is estimated both with and without the presence of the default provisions, holding all other assumptions constant. The resulting difference between the

two

estimated fair values is the estimated fair value of the default provisions, or the contingent put option. Changes to the estimated fair value of these liabilities are recorded in interest income and other income (expense), net in the Consolidated Statements of Comprehensive Loss. The fair value of the underlying debt facility is estimated by calculating the expected cash flows in consideration of an estimated probability of default and expected recovery rate in default, and discounting such cash flows back to the reporting date using a risk-free rate. As of

December

31,

2016,

the Company also held a Level III liability associated with warrants, or PIPE warrants, issued in connection with the Company’s private placement equity offering, completed in

June 2012.

For a detailed description, see Note

“Stockholders’ Equity”. The PIPE warrants were considered a liability and were valued using the Black-Scholes option-pricing model, the inputs for which included exercise price of the PIPE warrants, market price of the underlying common shares, expected term, volatility based on a group of the Company’s peers and the risk-free rate corresponding to the expected term of the PIPE warrants. Changes to any of these inputs could have a significant impact to the estimated fair value of the PIPE warrants.

The following table sets forth the fair value of the Company

’s financial assets and liabilities by level within the fair value hierarchy (in thousands):

	As of December 31 , 201 7
	Fair Value		Level I		Level II		Level III
Assets
U.S. government agency obligations	$	30,704	$	—	$	30,704	$	—
Total assets measured at fair value	$	30,704	$	—	$	30,704	$	—

Liabilities
Contingent put option liability	$	207	$	—	$	—	$	207
Total liabilities measured at fair value	$	207	$	—	$	—	$	207

	As of December 31 , 2016
	Fair Value		Level I		Level II		Level III
Assets
U.S. government agency obligations	$	30,477	$	—	$	30,477	$	—
Total assets measured at fair value	$	30,477	$	—	$	30,477	$	—

Liabilities
PIPE warrants	$	288		—		—	$	288
Contingent put option liability		124		—		—		124
Total liabilities measured at fair value	$	412	$	—	$	—	$	412

The following table sets forth a summary of the changes in the fair value of the Company

’s Level III financial liabilities for the years ended

December

31,

2017

and

2016

(in thousands):

	Year Ended December 31, 201 7
Fair value —beginning of period	$	412
Expiration of fair value of PIPE warrants		(288	)
Change in fair value of contingent put option associated with Original Loan Agreement		83
Fair value —end of period	$	207

	Year Ended December 31, 201 6
Fair value —beginning of period	$	1,179
Change in fair value of PIPE warrants		(625	)
Change in fair value of contingent put option associated with Original Loan Agreement		(142	)
Fair value —end of period	$	412

Note 3 - Inventories

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Inventory Disclosure [Text Block]

Inventories

Inventories consist of finished goods, raw materials and work in process and are stated at the lower of cost or market and consist of the following (in thousands):

	As of December 31,
	201 7		201 6
Raw materials	$	702	$	1,126
Work-in-process		254		296
Finished goods		—		732
Inventories	$	956	$	2,154

The Company periodically evaluates the carrying value of inventory on hand for potential excess amount over demand using the same lower of cost or market approach as that used to value the inventory.

During the year ended

December 31, 2017,

the Company recorded an inventory impairment charge of

$0.4

million, primarily for ZALVISO raw materials inventory on hand, plus related purchase commitments.

Note 4 - Property and Equipment

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Property, Plant and Equipment Disclosure [Text Block]

Property and Equipment

Property and equipment consist of the following (in thousands):

	As of December 31,
	201 7			201 6
Laboratory equipment	$	3,920		$	3,775
Leasehold improvements		4,469			4,469
Computer equipment and software		241			266
Construction in process		9,703			7,816
Tooling		1,109			1,074
Furniture and fixtures		47			48
		19,489			17,448
Less accumulated depreciation and amortization		(8,438	)		(6,736	)
Property and equipment, net	$	11,051		$	10,712

Depreciation and amortization

expense was

$1.7

million,

$2.1

million and

$2.0

million during the years ended

December

31,

2017,

2016

and

2015,

respectively. Property and equipment, net in the Consolidated Balance Sheets at

December 31, 2017

and

2016,

includes

$0.3

million and

$1.5

million, respectively, related to certain modifications the Company has made at Patheon Pharmaceutical Inc.’s, or Patheon’s, Cincinnati facility under the terms of the Capital Expenditure and Equipment Agreement, or the Capital Agreement.

Note 5 - U.S. Department of Defense Contract	12 Months Ended
Note 5 - U.S. Department of Defense Contract	Dec. 31, 2017
Notes to Financial Statements
Long-term Contracts or Programs Disclosure [Text Block]	5. U.S. Department of Defense Funding On May 11, 2015, the Company entered into an award contract (referred to as the DoD Contract) supported by the Clinical and Rehabilitative Medicine Research Program, or CRMRP, of the United States Army Medical Research and Materiel Command, or the USAMRMC, within the U.S. Department of Defense, or the DoD, in which the DoD agreed to provide up to $17.0 million to the Company in order to support the development of DSUVIA (sufentanil sublingual tablet, 30 mcg), a proprietary, non-invasive, single-use tablet in a disposable, pre-filled single-dose applicator, or SDA, for the treatment of moderate-to-severe acute pain. Under the terms of the DoD Contract, the DoD has reimbursed the Company for costs incurred for development, manufacturing, regulatory and clinical costs outlined in the DoD Contract, including reimbursement for certain personnel and overhead expenses. The period of performance under the DoD Contract began on May 11, 2015. The DoD Contract gives the DoD the option to extend the term of the DoD Contract and provide additional funding for the research. On March 2, 2016, the DoD Contract was amended to approve enrollment of additional patients in the SAP302 study, approve the addition of the SAP303 study, and extend the DoD Contract period of performance by four months from November 10, 2016 to March 9, 2017, to accommodate the increased SAP302 patient enrollment and the SAP303 study. The costs for these changes were included within the current DoD Contract value. On March 9, 2017, the DoD Contract was amended to incorporate additional activities including the development and testing of packaging changes; additional stability testing; and preparation for any FDA advisory committee meeting for DSUVIA. The amendment also extends the DoD Contract period of performance by 11 months through February 28, 2018 to accommodate these additional activities. At December 31, 2017, the additional activities as outlined under the DoD Contract through February 28, 2018 were substantially complete. On February 28, 2018, the DoD contract was amended to incorporate additional services in the amount of $0.5 million and to extend the contract period by twelve months through February 28, 2019. If DSUVIA is approved by the FDA, the DoD has the option to purchase a certain number of units of commercial product pursuant to the terms of the DoD Contract. Revenue is recognized based on expenses incurred by the Company in conducting research and development activities, including overhead, as set forth in the agreement. Revenue attributable to the work performed under the DoD Contract, recorded as Contract and other revenue in the Consolidated Statements of Comprehensive Loss, was $0.9 million, $10.9 million and $4.4 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Note 6 - Collaboration Agreement

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Collaborative Arrangement Disclosure [Text Block]

Collaboration Agreement

As described in Note

“Organization and Summary of Significant Accounting Policies,”

the Company has entered into amendments to the Agreements with Grünenthal related to ZALVISO. In the Amended Agreements, the parties amended the Product supply configurations and packaging of Product components and accessories, and associated pricing therefor, which the Company will manufacture and supply to Grünenthal for the Territory. The parties agreed to increase the pricing of the Product components and accessories in exchange for a reduction of

$5.5

million in the total milestone payments due from Grünenthal contingent upon achieving specified net sales targets from a total of

$171.5

million to

$166.0

million. The parties also updated the development plan for the Product in the Territory, providing for additional near-term development services to be rendered by AcelRx in exchange for payments by Grünenthal of

$0.7

million. In accordance with the terms of the Amended MSA, AcelRx also received a binding Product forecast from Grünenthal for approximately

$3.7

million, which was fully delivered by the end of

2016.

Amended License Agreement

Under the terms of the Amended License Agreement, Grünenthal has the exclusive right to commercialize the Product in the Field in the Territory. The Company retains control of clinical development, while Grünenthal and the Company will be responsible for certain development activities pursuant to a development plan as agreed between the parties. The Company will

not

receive separate payment for such development activities, apart from the

$0.7

million included under the Amended Agreements. Grünenthal is exclusively responsible for marketing approval applications and other regulatory filings relating to the sufentanil sublingual tablet drug cartridge for the Product in the Field in the Territory, while the Company is responsible for the CE Mark and other regulatory filings relating to device portions of the

Product. A CE Mark for ZALVISO was obtained in the

fourth

quarter of

2014

which specifies AcelRx as the device design authority and manufacturer. In

September 2015,

the European Commission approved the MAA for ZALVISO for the

EU member states as well as for the EEA. In

April 2016,

Grünenthal completed the

first

commercial sale of ZALVISO.

The Company received an upfront non-refundable cash payment of

$30.0

million in

December 2013,

and a milestone payment of

$5.0

million related to the MAA submission in the

third

quarter of

2014,

and an additional

$15.0

million milestone payment upon the EC approval of the MAA for ZALVISO, which was approved in

September 2015.

Under the Amended License Agreement, the Company is eligible to receive approximately

$194.5

million in additional milestone payments, based upon successful regulatory and product development efforts (

$28.5

million) and net sales target achievements (

$166.0

million). Grünenthal will also make tiered royalty and supply and trademark fee payments in the mid-teens up to the mid-twenties percent range, depending on the level of sales achieved, on net sales of ZALVISO.

A portion of the tiered royalty payment, exclusive of the supply and trademark fee payments, will be paid to PDL in connection with the Royalty Monetization. For additional information on the Royalty Monetization with PDL, see Note

“Liability Related to Sale of Future Royalties”. Unless earlier terminated, the Amended License Agreement continues in effect until the expiration of the obligation of Grünenthal to make royalty and supply and trademark fee payments, which supply and trademark fee continues for so long as the Company continues to supply the Product to Grünenthal. The Amended License Agreement is subject to earlier termination in the event the parties mutually agree, by a party in the event of an uncured material breach by the other party, upon the bankruptcy or insolvency of either party, or by Grünenthal for convenience.

Amended MSA

Under the terms of the Amended MSA, the Company will manufacture and supply the Product for use in the Field for the Territory exclusively for Grünenthal. Grünenthal shall purchase from AcelRx, during the

first

five

years after the effective date of the MSA,

December 16, 2013

through

December 15, 2018,

100%

and thereafter

80%

of Grünenthal’s and its sublicensees’ and distributors’ requirements of Product for use in the Field for the Territory. The Product will be supplied at prices approximating the Company’s manufacturing cost, subject to certain caps, as defined in the MSA Amendment. The MSA Amendment requires the Company to use commercially reasonable efforts to enter stand-by contracts with

third

parties providing significant supply and manufacturing services and, under certain specified conditions, permits Grünenthal to use a

third

party back-up manufacturer to manufacture the Product for Grünenthal’s commercial sale in the Territory.

Unless earlier terminated, the Amended MSA continues in effect until the later of the expiration of the obligation of Grünenthal to make royalty and supply and trademark fee payments or the end of any transition period for manufacturing obligations due to the expiration or termination of the Amended License Agreement. The Amended MSA is subject to earlier termination in connection with certain termination events in the Amended License Agreement, in the event the parties mutually agree, by a party in the event of an uncured material breach by the other party or upon the bankruptcy or insolvency of either party.

The Company identified the following

four

significant non-contingent performance deliverables under the original Agreements:

) intellectual property (license),

) the obligation to provide research and development services,

) the significant and incremental discount on the manufacturing of

ZALVISO for commercial purposes, and

) the obligation to participate on the joint steering committee.

At the time the Amended Agreements were executed, with the exception of the intellectual property license, these obligations remained partially undelivered. Additionally, the Company identified the following

three

performance deliverables under the License Amendment and the MSA Amendment:

) the obligation to provide additional research and development services,

) the obligation to provide

ZALVISO demonstration device systems, and

) the obligation to manufacture and deliver Product under the binding forecast. The Company determined that the License Amendment and MSA Amendment were modifications to the original Agreements.

The Company considered the provisions of the multiple-element arrangement guidance in determining whether the deliverables outlined above have standalone value and thus should be treated as separate units of accounting. The Company

’s management determined that the license under the original License Agreement had standalone value and represented a separate unit of accounting because the rights conveyed permitted Grünenthal to perform all efforts necessary to commercialize and begin selling the product upon regulatory approval. In addition, Grünenthal has the appropriate development, regulatory and commercial expertise with products similar to the product licensed under the agreement and has the ability to engage

third

parties to manufacture the product allowing Grünenthal to realize the value of the license without receiving any of the remaining deliverables. Grünenthal can also sublicense its license rights to

third

parties. Also, the Company’s management determined that the research and development services, ZALVISO demonstration device systems, joint steering committee participation, the significant and incremental discount on the manufacturing of ZALVISO, and the obligation to manufacture and deliver Products each represent individual units of accounting, as Grünenthal could perform such services and/or could acquire these on a separate basis.

The Company believes that

none

of the deliverables have VSOE

, or sufficient TPE of selling price, as

none

of them have been sold separately by the Company, and as there is only limited information about

third

party pricing for similar deliverables. Accordingly, the Company developed BESP for each deliverable in order to allocate the noncontingent arrangement consideration to the units of accounting, based on current information available as of the modification date.

The Company

’s management determined the best estimate of selling price for the license based on Grünenthal’s estimated future cash flows arising from the arrangement. Embedded in the estimate were significant assumptions regarding regulatory expenses, revenue, including potential customer market for the product and product price, costs to manufacture the product and the discount rate. The Company’s management determined the best estimate of selling price of the research and development services and committee participation based on the nature and timing of the services to be performed and in consideration of personnel and other costs incurred in the delivery of the services. For the discount on manufacturing services, the Company’s management estimated the selling price based on the market level of contract manufacturing margin it could have received if it were engaged to supply products to a customer in a separate transaction, the estimated cost of manufacturing, and the anticipated volume of Grünenthal’s orders over the course of the agreement, to which the discount would apply. For the ZALVISO demonstration devices and the obligation to manufacture and deliver Product, the Company’s management estimated the selling price based on the binding volume of such devices and Products, the estimated cost of manufacturing, and the market level of contract manufacturing margin. BESP of the license, research and development and committee participation services and the discount on manufacturing services were updated at the time the Amended Agreements were executed for purposes of allocating the amended arrangement consideration.

The Amended Agreements entitle the Company to receive additional payments upon the achievement of certain development and sales milestones. Based on ASC Topic

605

28,

Revenue Recognition — Milestone Method

, the Company evaluates contingent milestones at inception or modification of the agreement, and recognizes consideration that is contingent upon the achievement of a milestone in its entirety as revenue in the period in which the milestone is achieved only if the milestone is considered substantive in its entirety. Milestones are events which have the following characteristics: (i) they can be achieved based in whole or in part on either the Company’s performance or on the occurrence of a specific outcome resulting from the Company’s performance, (ii) there was substantive uncertainty at the date the agreement was entered into that the event would be achieved and, (iii) they would result in additional payments due to the Company. A milestone is considered substantive if the following criteria are met: (i) the consideration is commensurate with either (

) the entity’s performance to achieve the milestone, or (

) the enhancement of the value of the delivered item (s) as a result of a specific outcome resulting from the entity’s performance to achieve the milestone, (ii) the consideration relates solely to past performance and, (iii) the consideration is reasonable relative to all of the other deliverables and payment terms, including other potential milestone consideration, within the arrangement.

The substantive milestone payments will be recognized as revenue in their entirety upon the achievement of each substantive milestone. Based on the criteria noted above, the identified substantive milestones in the original Agreements pertain to post approval product enhancements, expanded market opportunities and manufacturing efficiencies for

ZALVISO. Each of these potential achievements is based primarily on the Company’s performance and involves substantive uncertainty as achievement of these milestones requires future research, development and regulatory activities, which are inherently uncertain in nature. The Company determined that the consideration for each milestone was commensurate with the Company’s performance to achieve the milestone, including future research, development, manufacturing and regulatory activities and that the consideration is reasonable relative to all of the other deliverables and payments within the arrangement. Aggregate potential payments for these milestones total

$28.5

million.

In addition to substantive milestones,

two

milestones associated with the original Agreements were deemed

not

to be substantive. These milestones pertain to regulatory developments for

ZALVISO in Europe, which the Company’s management deemed to be

not

substantive due to the high likelihood of achievement, both at inception of the original Agreements and at the time the Amended Agreements were executed. Aggregate potential payments for these milestones totaled

$20.0

million. In

July 2014,

Grünenthal submitted an MAA to the EMA for ZALVISO for the management of acute moderate-to-severe post-operative pain in adult patients, triggering the

first

of these

two

milestones, a cash payment of

$5.0

million. In

September

2015,

the MAA was approved by the European Commission, triggering the

second

of these

two

milestones, a cash payment of

$15.0

million. Amounts received under these non-substantive milestones were allocated to performance deliverables based on the relative selling price method and recognized as appropriate for such deliverables.

The Amended Agreements also include milestone payments related to specified net sales targets, totaling

$166.0

million. These milestones do

not

meet the definition of a milestone under ASU

2010

because the achievement of these milestones is solely dependent on counter-party performance and

not

on any performance obligations of the Company.

At the time the Amended Agreements were executed, approximately

$33.3

million of revenue had been recognized, and

$1.7

million remained unrecognized from the aggregate to-date consideration of

$35.0

million received under the original Agreements. Upon execution of the Amended Agreements, the Company updated the allocation of this arrangement consideration, along with the consideration owed under the Amended Agreements totaling

$54.4

million, consisting of

$0.7

million related to research and development services and the demonstration device systems, and

$3.7

million related to the Product binding purchase forecast, to all of the identified deliverables in the arrangement (both delivered and undelivered) using their relative selling prices. Further, the

$15.0

million non-substantive milestone achieved in

September

2015

was also allocated to the deliverables in the same manner. As a result of such allocations, additional amounts of

$13.2

million and

$0.5

million were allocated to the previously delivered license and research and development and committee participation services, respectively. A total of

$4.4

million was allocated to the significant and incremental discount on manufacturing services, and is expected to be recognized over the period such discount is made available to Grünenthal, beginning in

February 2016,

on a straight-line basis over the estimated period through

2029.

An additional

$0.2

million has been allocated to committee participation services and is recognized on a straight-line basis over the performance obligation period extending through

2018.

A total of

$2.3

million was allocated to manufacturing services for the binding forecast of Products. The remaining

$0.5

million was allocated to the additional research and development services under the Amended License Agreement and demonstration device systems, and manufacturing and delivery of the Products, and will be recognized as those services are performed or as the devices are delivered, as applicable.

Below is a summary of revenue recognized under the Amended Agreements during the years ended

December 3

2017,

2016

and

2015

(in thousands):

	Years Ended December 31,
	201 7		201 6		2015
License	$	—	$	—	$	13,167
Product sales		6,673		5,742		—
Joint steering committee, research and development services and demonstration devices		269		688		1,690
Non-cash royalty revenue related to Royalty Monetization (See Note 8)		151		7		—
Royalty revenue		50		3		—
Total	$	7,143	$	6,440	$	14,857

As of

December 31,

201

the Company had current and noncurrent portions of the deferred revenue balance under the Amended Agreements of

$0.4

million and

$3.5

million, respectively.

Note 7 - Long-term Debt

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Long-term Debt [Text Block]

Long-Term Debt

Amended

Loan and Security Agreement

December

16,

2013,

AcelRx entered into an Amended and Restated Loan and Security Agreement with Hercules Technology II, L.P. and Hercules Capital, Inc., formerly known as Hercules Technology Growth Capital, Inc., together, the Lenders, or the Original Loan Agreement, under which the Company was provided the ability to borrow up to

$40.0

million in

three

tranches. The loans were represented by secured convertible term promissory notes, collectively, the

2013

Notes. The Original Loan Agreement amended and restated the prior Loan and Security Agreement between the Company and the Lenders dated as of

June

29,

2011.

The Company borrowed the

first

tranche of

$15.0

million upon closing of the transaction on

December

16,

2013,

and the

second

tranche of

$10.0

million on

June 16, 2014

. The Company used approximately

$8.6

million of the proceeds from the

first

tranche to repay its obligations under the prior Loan and Security Agreement with the Lenders. The Company recorded the new debt at an estimated fair value of

$24.9

million as of

December 31, 2014.

In connection with the Original Loan Agreement, the Company issued a warrant to each Lender which, collectively, are exercisable for an aggregate of

176,730

shares of common stock and each carried an exercise price of

$6.79

per share.

September

24,

2014,

the Company entered into Amendment

No.

to the Original Loan Agreement with the Lenders. Amendment

No.

extended the time period under which the Company could draw down the

third

tranche, of up to

$15.0

million, from

March

15,

2015

August

2015,

subject to the Company obtaining approval for ZALVISO from the FDA. The Company did

not

receive FDA approval of ZALVISO by

August 1, 2015

and as such, did

not

have access to the

third

tranche.

September 18, 2015,

concurrently with the closing of the Royalty Monetization, the Company entered into a Consent and Amendment

No.

or Amendment

No.

to the Original Loan Agreement with the

Lenders. Amendment

No.

includes an interest only period from

October 1, 2015

through

March 31, 2016,

with further extension to

September 30, 2016

upon satisfaction of certain conditions. These conditions were satisfied in the

third

quarter of

2015

and the interest only period was extended through

September 30, 2016.

Loans under the Original Loan Agreement were scheduled to mature on

October 1, 2017.

In connection with Amendment

No.

the Company reduced the exercise price of the warrants already held by the Lenders, which are exercisable for an aggregate of

176,730

shares of Common Stock, from the previous exercise price of

$6.79

per share to

$3.88

per share.

September 30, 2016,

the Company entered into Amendment

No.

to the Original Loan Agreement w

ith the Lenders. Among other things, Amendment

No.

extended the interest-only period from

October 1, 2016

April 1, 2017.

In connection with Amendment

No.

the Company reduced the exercise price of the existing warrants held by the Lenders, which are exercisable for an aggregate of

176,730

shares of common stock, from the previous exercise price of

$3.88

per share to

$3.07

per share.

March 2, 2017,

the Company amended and restated the Original Loan Agreement with the Lenders, which is referred to as the Amended Loan Agreement. Pursuant to the Amended Loan Agreement,

the Company borrowed the

first

tranche of approximately

$20.5

million upon closing of the transaction on

March 2, 2017,

which is represented by secured term promissory notes, or the Notes. The Company used all of the proceeds from the

first

tranche to repay its obligations under the Original Loan Agreement, including a final payment of

$1.7

million made on

October 1, 2017.

The interest rate is calculated at a rate equal to the greater of either (i)

9.55%

plus the prime rate as reported from time to time in The Wall Street Journal minus

3.50%,

and (ii)

9.55%.

Payments under the Amended Loan Agreement were interest-only until

October 1, 2017

followed by equal monthly payments of principal and interest through the scheduled maturity date of

March 1, 2020.

A final payment equal to

6.5%

of the aggregate principal amount of loans funded under the Amended Loan Agreement, or End of Term Fee, or EOT Fee, will be due on the earliest of (i) the maturity date, (ii) prepayment in full of the loans (other than by a refinancing with Hercules) or (iii) the date on which the loans under the Amended Loan Agreement become due and payable. The Company’s obligations under the Amended Loan Agreement are secured by a security interest in substantially all of its assets, other than its intellectual property.

If the Company prepays the loans under the Amended Loan Agreement prior to the maturity date, it will pay Hercules a prepayment charge, based on a percentage of the then outstanding principal balance, equal to

if the prepayment occurs prior to

March 2, 2018,

if the prepayment occurs after

March 2, 2018,

but prior to

March 2, 2019,

if the prepayment occurs after

March 2, 2019.

The Amended Loan Agreement includes customary affirmative and restrictive covenants, but does

not

include any financial maintenance covenants, and also includes standard events of default, including payment defaults, breaches of covenants following any applicable cure period, a material impairment in the perfection or priority of Hercules

’ security interest or in the value of the collateral, and events relating to bankruptcy or insolvency. Upon the occurrence of an event of default, a default interest rate of an additional

may

be applied to the outstanding loan balances, and Hercules

may

declare all outstanding obligations immediately due and payable and take such other actions as set forth in the Amended Loan Agreement.

Upon an event of default, including a change of control,

Hercules has the option to accelerate repayment of the Amended Loan Agreement, including payment of any applicable prepayment charges. This option is considered a contingent put option liability, as the holder of the loan has the ability to exercise the option in the event of default, and is considered an embedded derivative, which must be valued and separately accounted for in the Company’s financial statements. As the Original Loan Agreement entered into on

December 16, 2013

was considered an extinguishment, the contingent put option liability associated with the prior Loan and Security Agreement, which had an estimated fair value of

$32

at the time of the amendment, was written off as a part of the loss on extinguishment, and a new contingent put option liability was established. As of

December 31, 2017

and

2016,

the estimated fair value of the contingent put option liability was

$0.2

million and

$0.1

million, respectively, which was determined by using a risk-neutral valuation model, wherein the fair value of the underlying debt facility is estimated both with and without the presence of the default provisions, holding all other assumptions constant. The resulting difference between the

two

estimated fair values is the estimated fair value of the default provisions, or the contingent put option. The fair value of the underlying debt facility is estimated by calculating the expected cash flows in consideration of an estimated probability of default and expected recovery rate in default, and discounting such cash flows back to the reporting date using a risk-free rate. The contingent put option liability is revalued at the end of each reporting period and any change in the fair value is recognized in interest income and

other income (expense), net in the Consolidated Statements of Comprehensive Loss.

The Company

performed an analysis of Amendments

No.

and

No.

to determine if each amendment was a modification or extinguishment of the debt under the Original Loan Agreement. The Company assumed immediate prepayment of both the pre-modification debt and post-modification debt, including the change in the fair value due to the warrant amendments, and concluded that Amendments

No.

and

No.

were each modifications rather than extinguishments of the debt.

The accrued balance due under the

Amended Loan Agreement was

$19.1

million at

December 31, 2017

and was

$21.5

million under the Original Loan Agreement at

December 31, 2016.

Interest expense related to the Amended Loan Agreement was

$3.3

million for the year ended

December 31, 2017

and was

$2.8

million and

$3.0

million under the Original Loan Agreement for the years ended

December 31, 2016

and

2015,

respectively.

Future Payments on Long-Term Debt

The following table summarizes our outstanding future payments associated with the Company

’s long-term debt as of

December

31,

2017

(in thousands):

20 18	$	9,350
2019		9,350
20 20		3,704
Total payments		22,404
Less amount representing interest		(2,420	)
Notes payable, gross		19,984
Unamortized portion of final payment		(741	)
Unamortized discount on notes payable		(147	)
Long-term debt		19,096
Less current portion of notes payable, including unamortized discount		(7,727	)
Long-term debt, current portion	$	11,369

Note 8 - Liability Related to Sale of Future Royalties

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Liability Related to Sale of Future Royalties

September 18, 2015,

the Company consummated the Royalty Monetization, in which it sold certain royalty and milestone payment rights to its newly formed wholly owned subsidiary, ARPI LLC, pursuant to a Purchase and Sale Agreement, or PSA. Subsequently, ARPI LLC sold the royalty and milestone payment rights to PDL for an upfront cash purchase price of

$65.0

million, subject to a capped amount of

$195.0

million pursuant to the Subsequent Purchase and Sale Agreement, or SPSA. Under the SPSA, PDL will receive

75%

of the European royalties under the Amended License Agreement as well as

80%

of the

first

four

commercial milestones, worth

$35.6

million (or

80%

$44.5

million), subject to the capped amount. The Company is entitled to receive

25%

of the royalties,

20%

of the

first

four

commercial milestones,

100%

of the remaining commercial milestones and all remaining development milestones of

$43.5

million, including the

$15.0

million payment for the EC approval of the MAA for ZALVISO.

The Company and ARPI LLC continue to retain certain duties and obligations under the Amended License Agreement. These include the collection of the royalty and milestones amounts due and enforcement of related provisions under the Amended License Agreement, among others. In addition, the Company must prepare a quarterly distribution report relating to the Amended License Agreement, containing among other items, the amount of royalty and milestone payments received, reimbursable expenses and set-offs. The Company and ARPI LLC must also provide PDL with notice of certain communications, events or actions with respect to the Amended License Agreement and infringement of any underlying intellectual property.

The Company has significant continuing involvement in the Royalty Monetization primarily due to an obligation to act as the intermediary for the supply of

ZALVISO to

Grünenthal. Under the relevant accounting guidance, because of its significant continuing involvement, the Royalty Monetization has been accounted for as a liability that will be amortized using the interest method over the life of the arrangement. In order to determine the amortization of the liability, the Company is required to estimate the total amount of future royalty

and milestone payments to be received by PDL and payments the Company is required to make to PDL, up to a capped amount of

$195.0

million, over the life of the arrangement. The sum of the capped amount of

$195.0

million, less the

$61.2

million of net proceeds the Company received will be recorded as interest expense over the life of the liability. Consequently, the Company imputes interest on the unamortized portion of the liability and records interest expense. The Company’s estimate of the interest rate under the arrangement is based on the amount of royalty and milestone payments expected to be received by PDL over the life of the arrangement. The Company’s estimate of this total interest expense resulted in an effective annual interest rate of approximately

14%.

The Company will periodically assess the expected royalty and milestone payments using a combination of historical results, internal projections and forecasts from external sources. To the extent such payments are greater or less than our initial estimates or the timing of such payments is materially different than our original estimates, the Company will prospectively adjust the amortization of the liability and the interest rate.

The following table shows the activity within the liability account during the year ended

December 31,

201

(in thousands):

	Year ended December 31, 201 7			Period from inception to December 31, 201 7
Liability related to sale of future royalties — beginning balance	$	72,987		$	—
Proceeds from sale of future royalties		—			61,184
Non-cash royalty revenue		(120	)		(127	)
Non-cash interest expense recognized		10,721			22,531

Liability related to sale of future royalties as of December 31, 2017		83,588			83,588
Less: current portion		(604	)		(604	)
Liability related to sale of future royalties — net of current portion	$	82,984		$	82,984

Estimated non-cash royalty revenue

$31.0

thousand recognized in the

fourth

quarter of

2017

has

not

yet been remitted to PDL and therefore is

not

included in the table above.

As royalties are remitted to PDL from ARPI LLC, as described in Note

“Organization and Summary of Significant Accounting Policies,” the balance of the liability will be effectively repaid over the life of the agreement. The Company will record non-cash royalty revenues and non-cash interest expense within its Consolidated Statements of Comprehensive Loss over the term of the Royalty Monetization.

Note 9 - Warrants	12 Months Ended
Note 9 - Warrants	Dec. 31, 2017
Notes to Financial Statements
Warrants Disclosure [Text Block]	9. Warrants Amended and Restated Loan Agreement Warrants In connection with the Original Loan Agreement, executed in December 2013, the Company issued warrants to the Lenders which were exercisable for an aggregate of 176,730 shares of common stock with an exercise price of $6.79 per share, or the Warrants. In connection with Amendment No. 2 to the Original Loan Agreement, the Company reduced the exercise price of the warrants already held by the Lenders from the previous exercise price of $6.79 per share to $3.88 per share, or the First Warrant Amendments. In connection with Amendment No. 3 to the Original Loan Agreement, the Company reduced the exercise price of the warrants already held by the Lenders from the previous exercise price of $3.88 per share to $3.07 per share, or the Second Warrant Amendments. Each Warrant may be exercised on a cashless basis. The Warrants are exercisable for a term beginning on the date of issuance and ending on the earlier to occur of five years from the date of issuance or the consummation of certain acquisitions of the Company as set forth in the Warrants. The number of shares for which the Warrants are exercisable and the associated exercise price are subject to certain proportional adjustments as set forth in the Warrants. The Company estimated the fair value of these Warrants as of the issuance date to be $1.1 million, which was used in the estimating of the fair value of the amended debt instrument and was recorded as equity. The fair value of the Warrants was calculated using the Black-Scholes option-valuation model, and was based on the original strike price of $6.79, the stock price at issuance of $9.67, the five -year contractual term of the warrants, a risk-free interest rate of 1.55%, expected volatility of 71% and 0% expected dividend yield. The Company estimated the fair value of the modification of the First Warrant Amendments, as of the issuance date to be $0.1 million, which was used in estimating the fair value of the amended debt instrument in September 2015 and was recorded as equity, as well as the Second Warrant Amendments, which fair value was estimated to be $45.0 thousand at the issuance date, and which was used in estimating the fair value of the amended debt instrument in September 2016 and was recorded as equity. As of December 31, 2017, warrants to purchase 176,730 shares of common stock issued to the Lenders had not been exercised and were still outstanding. These warrants expire in December 2018. 2012 Private Placement Warrants In connection with the Private Placement, completed in June 2012, the Company issued PIPE warrants to purchase up to 2,630,103 shares of common stock. The per share exercise price of the PIPE warrants was $3.40 which equals the closing consolidated bid price of the Company ’s common stock on May 29, 2012, the effective date of the Purchase Agreement. The PIPE warrants issued in the Private Placement became exercisable six months after the issuance date, and expire on the five year anniversary of the initial exercisability date. Under the terms of the PIPE warrants, upon certain transactions, including a merger, tender offer, sale of all or substantially all of the assets of the Company or if a person or group shall become the owner of 50% of the Company’s issued and outstanding common stock, which is outside of the Company’s control, each PIPE warrant holder may elect to receive a cash payment in exchange for the warrant, in an amount determined by application of the Black-Scholes option-pricing model. Accordingly, the PIPE warrants were recorded as a liability at fair value, as determined by the Black-Scholes option-pricing model, and then marked to fair value each reporting period, with changes in estimated fair value recorded through the Consolidated Statements of Comprehensive Loss in interest income and other income (expense), net. The Black-Scholes assumptions used to value the PIPE warrants are disclosed in Note 2 “Investments and Fair Value Measurement.” Upon execution of the Purchase Agreement, the fair value of the PIPE warrants was estimated to be $5.8 million, w hich was recorded as a liability. The change in fair value for the years ended December 31, 2017, 2016 and 2015, which was recorded as other income, was $0.3 million, $0.6 million and $2.1 million, respectively. During the year ended December 31, 2017, 512,456 warrants expired unexercised. During the year ended December 31, 2015, PIPE warrants to purchase 847,058 shares were net exercised for 527,101 shares of common stock.

Note 10 - Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Commitments and Contingencies Disclosure [Text Block]

10.

Commitments and

Contingencies

Operating Leases

December 2011,

the Company entered into a non-cancelable lease agreement with Metropolitan Life Insurance Company, or the Landlord, referred to as the Existing Lease, for approximately

13,787

square feet of office and laboratory facilities located at

301

Galveston Drive, Redwood City, California, or the Current Premises, which serve as the Company headquarters, effective

April 2012.

Rent expense from the facility lease is recognized on a straight-line basis from the inception of the lease in

December 2011,

the early access date, through the end of the lease.

May 2014,

the Company entered into an amendment, or the Lease Amendment, to the Existing Lease for the Current Premises. Pursuant to the Lease Amendment, the term of the Existing Lease

was extended for a period of

twenty

(

) months and

twenty-two

(

) days and expiring on

January 31, 2018,

unless sooner terminated pursuant to the terms of the Existing Lease. In addition, the Lease Amendment included a new lease on an additional approximately

12,106

square feet of office space located at

351

Galveston Drive in Redwood City, California, or the Expansion Space, which is adjacent to the Current Premises. The new lease for the Expansion Space has a term of

months commencing on

August 1, 2014,

and expiring on

January 31, 2018.

October 2, 2015,

the Company executed an agreement to sublease

approximately

11,871

square feet of the Expansion Space for a term of

months commencing on

December 1, 2015.

The sublessee was entitled to abatement of the

first

two

monthly installments of rent. Subsequent monthly installments of rent start at a rental rate of

$2.05

per square foot (subject to agreed nominal increases). Minimum rents received under this sublease were

$0.3

million for the year ended

December 31, 2017

and are expected to be

$25.0

thousand for the year ending

December 31, 2018.

June 14, 2017,

the

Company entered into a

second

amendment, or the Second Lease Amendment, to the Existing Lease, and as amended by the Second Lease Amendment, the Lease, with the Landlord, for approximately

25,893

square feet located at

301

–

351

Galveston Drive, Redwood City, California, or the Current Premises and the Expansion Space, together, the Premises. Pursuant to the Second Lease Amendment, the term of the Existing Lease has been extended for a period of

seventy-two

(

) months, or the Extended Term, beginning

February 1, 2018

and expiring

January 31, 2024,

or the Expiration Date, unless sooner terminated pursuant to the terms of the Lease.

Pursuant to the Lease Amendment, the Company will pay on a monthly basis annual rent of approximately

$1.2

million, with annual increases each

-month period beginning

February 1

, and the

first

two

months to be abated provided that the Company is

not

in default thereunder. In addition, the Company will pay the Landlord specified percentages of certain operating expenses related to the leased facility incurred by the Landlord.

Rent

expense was

$0.6

million,

$0.3

million and

$0.6

million for the Premises during the years ended

December

31,

2017,

2016

and

2015,

respectively.

Future minimum payments under the

Lease as of

December

31,

2017,

are as follows (in thousands):

Year Ending December 31:
201 8	$	959
2019		1,231
2020		1,268
2021		1,305
2022		1,345
Thereafter		1,501
Total minimum payments	$	7,609

Litigation

From time to time the Company

may

be involved in legal proceedings arising in the ordinary course of business. The Company does

not

have contingent liabilities established for any litigation matters.

Note 11 - Stockholders' Equity	12 Months Ended
Note 11 - Stockholders' Equity	Dec. 31, 2017
Notes to Financial Statements
Stockholders' Equity Note Disclosure [Text Block]	11. Stockholders ’ Equity Common Stock 201 6 ATM Agreement On June 21, 2016, the Company entered into a Controlled Equity Offering SM Sales Agreement, or the Sales Agreement, or 2016 ATM Agreement, with Cantor Fitzgerald & Co., or Cantor, as agent, pursuant to which the Company may offer and sell, from time to time through Cantor, shares of the Company’s common stock, or the Common Stock having an aggregate offering price of up to $40.0 million, or the Shares. The offering of Shares pursuant to the Sales Agreement will terminate upon the earlier of (a) the sale of all of the Shares subject to the Sales Agreement or (b) the termination of the Sales Agreement by Cantor or the Company, as permitted therein. The Company will pay Cantor a commission rate in the low single digits on the aggregate gross proceeds from each sale of Shares and have agreed to provide Cantor with customary indemnification and contribution rights. During the year ended December 31, 2017, the Company issued and sold 5.4 million shares of common stock pursuant to the 2016 ATM Agreement, for which the Company received net proceeds of approximately $15.7 million, after deducting commissions, fees and expenses of $0.5 million. Stock Plans 2006 Stock Plan In August 2006, the Company establi shed the 2006 Plan in which 342 shares of common stock were originally reserved for the issuance of incentive stock options, or ISOs, and nonstatutory stock options, or NSOs, to employees, directors or consultants of the Company. In February 2008, an additional 375 shares of common stock were reserved for issuance under the 2006 Plan and, in November 2009, an additional approximately 1.4 million shares of common stock were reserved for issuance under the 2006 Plan. Per the 2006 Plan, the exercise price of ISOs and NSOs granted to a stockholder who at the time of grant owns stock representing more than 10% of the voting power of all classes of the stock of the Company could not be less than 110% of the fair value per share of the underlying common stock on the date of grant. Effective upon the execution and delivery of the underwriting agreement for the Company’s IPO, no additional stock options or other stock awards may be granted under the 2006 Plan. 2011 Equity Incentive Plan In January 2011, the Board of Directors adopted, and the Company’s stockholders approved, the 2011 Equity Incentive Plan, or 2011 Incentive Plan, as a successor to the 2006 Plan. The 2011 Incentive Plan became effective immediately upon the execution and delivery of the underwriting agreement for the IPO on February 10, 2011. As of February 10, 2011, no more awards may be granted under the 2006 Plan, although all outstanding stock options and other stock awards previously granted under the 2006 Plan will continue to remain subject to the terms of the 2006 Plan. The approximately 52 shares reserved under the 2006 Plan that remained available for future grant at the time of the IPO were transferred to the share reserve of the 2011 Incentive Plan. The initial aggregate number of shares of the Company ’s common stock that may be issued pursuant to stock awards under the 2011 Incentive Plan is approximately 1.9 million shares, which number was the sum of (i) 52 shares remaining available for future grant under the 2006 Plan at the time of the execution and delivery of the underwriting agreement for the Company’s IPO, and (ii) an additional approximately 1.8 million new shares. Then, the number of shares of common stock reserved for issuance under the 2011 Incentive Plan will automatically increase on January 1st each year, starting on January 1, 2012 and continuing through January 1, 2020, by 4% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, or such lesser number of shares of common stock as determined by the Board of Directors. The term of the option is determined by the Board of Directors on the date of grant but shall not be longer than 10 years. Options under the 2011 Equity Incentive Plan generally vest over four years, and all options expire after 10 years. The Company issues new shares for settlement of vested restricted stock units and exercises of stock options. The Company does not have a policy of purchasing its shares relating to its share-based programs. 2011 Employee Stock Purchase Plan Additionally, in January 2011, the Board of Directors adopted, and the Company’s stockholders approved, the 2011 Employee Stock Purchase Plan, or the ESPP, which also became effective immediately upon the execution and delivery of the underwriting agreement for the IPO. Initially, 250 shares of the Company ’s common stock were authorized for issuance under the ESPP pursuant to purchase rights granted to the Company’s employees or to employees of any of its designated affiliates. The number of shares of the Company’s common stock reserved for issuance will automatically increase on January 1st each year, starting January 1, 2012 and continuing through January 1, 2020, in an amount equal to the lower of ( 1 ) 2% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, or ( 2 ) a number of shares of common stock as determined by the Board of Directors. If a purchase right granted under the ESPP terminates without having been exercised, the shares of the Company’s common stock not purchased under such purchase right will be available for issuance under the ESPP. As of December 31, 2017, 94,893 shares have been issued to employees and there are 1,041,249 shares available for issuance under the ESPP. The weighted average fair value of shares issued under the ESPP in 2017, 2016 and 2015 was $2.59, $2.98 and $4.48 per share, respectively.

Note 12 - Stock-based Compensation

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Disclosure of Compensation Related Costs, Share-based Payments [Text Block]

12.

Stock-Based Compensation

The Company recorded total stock-based compensation expense for stock options, stock awards and the ESPP as follows

(in thousands):

	December 31, 201 7		December 31, 201 6		December 31, 201 5
Cost of goods sold	$	324	$	302	$	67
Research and development		1,901		2,308		2,587
General and administrative		2,069		1,869		2,356
Total	$	4,294	$	4,479	$	5,010

The following table summarizes option activity under the

2011

Plan and

2006

Plan:

	Number of Stock Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
								(in thousands)
December 31, 2016		6,307,756		$	5.00
Granted		3,007,155			2.99
Forfeited		(438,519	)		4.28
Expired		(351,922	)		7.31
Exercised		(69,372	)		1.52
December 31, 2017		8,455,098		$	4.25		7.1	$	13
Vested and exercisable options —December 31, 2017		4,529,174		$	5.11		5.56	$	13
Vested and expected to vest —December 31, 2017		8,455,098		$	4.25		7.1	$	13

As of

December

31,

2017,

there were

2,368,992

shares available for future grant under the

2011

Plan. In

January 2018,

an additional

2,035,966

shares were authorized for issuance under the

2011

Incentive Plan.

Additional information regarding the Company

’s stock options outstanding and vested and exercisable as of

December

31,

2017

is summarized below:

			Options Outstanding						Options Vested and Exercisable
Exercise Prices			Number of Stock Options Outstanding		Weighted-Average Remaining Contractual Life (Years)		Weighted-Average Exercise Price per Share		Shares Subject to Stock Options		Weighted-Average Exercise Price per Share
$1.20	-	$2. 30		105,900		8.4	$	2.13		38,400	$	1.84
$2. 40	-	$3.77		5,592,633		7.7	$	3.10		1,948,300	$	3.17
$ 3.92	-	$6.60		2,060,565		5.7	$	5.45		1,880,190	$	5.36
$8.18	-	$10.55		696,000		6.2	$	10.28		662,284	$	10.28
				8,455,098		7.1	$	4.25		4,529,174	$	5.11

The weighted average grant-date fair value of options granted during the years ended

December

31,

2017,

2016

and

2015

was

$1.91,

$2.24

and

$2.69

per share, respectively. As of

December

31,

2017,

total stock-based compensation expense related to unvested options to be recognized in future periods was

$7.1

million which is expected to be recognized over a weighted-average period of

2.6

years. The grant date fair value of shares vested during the years ended

December

31,

2017,

2016

and

2015

was

$3.5

million,

$3.9

million and

$5.4

million, respectively. The total intrinsic value of options exercised during the year ended

December

31,

2017

was

$40

thousand. There were

option exercises during the year ended

December 31, 2016,

and the total intrinsic value of options exercised during the year ended

December 31, 2015

was

$1.3

million.

The Company used the following assumptions to calculate the fair value of each employee stock option:

	Year Ended December 31,
	201 7			201 6			201 5
Expected term (in years)	5.70			5.25	-	6.25	5.25	-	6.25
Risk-free interest rate	1.82%	-	2.09%	1.24%	-	1.47%	1.35%	-	1.82%
Expected volatility	73%			80%			72%
Expected dividend rate	0%			0%			0%

Note 13 - Restructuring Costs	12 Months Ended
Note 13 - Restructuring Costs	Dec. 31, 2017
Notes to Financial Statements
Restructuring and Related Activities Disclosure [Text Block]	13. Restructuring Costs On March 19, 2015, the Board of Directors of the Company, in connection with its efforts to reduce operating costs, conserve capital, focus the Company's financial and development resources on working with the FDA to seek marketing approval for ZALVISO, and continuing development of DSUVIA, implemented a cost reduction plan. The cost reduction plan reduced the Company’s workforce by 19 employees, approximately 36% of total headcount, in the first quarter of 2015. Employee termination benefits related to this restructuring, are charged to restructuring costs in the Consolidated Statements of Comprehensive Loss, and totaled $0.8 million in the year ended December 31, 2015. The restructuring liability was fully disbursed as of December 31, 2015.

Note 14 - Net Loss Per Share of Common Stock

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Earnings Per Share [Text Block]

14.

Net Loss per Share of Common Stock

The Company

’s basic net loss per share of common stock is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding for the period. The diluted net loss per share of common stock is computed by giving effect to all potential common stock equivalents outstanding for the period determined using the treasury stock method. For purposes of this calculation, options to purchase common stock and warrants to purchase common stock were considered to be common stock equivalents. In periods with a reported net loss, common stock equivalents are excluded from the calculation of diluted net loss per share of common stock if their effect is antidilutive.

The PIPE warrants expired during the year ended

December 31, 2017.

During the year ended

December 31, 2016,

the exercise price of the PIPE warrants exceeded the average of AcelRx’s closing share price in the period. As a result, the PIPE warrants were anti-dilutive during the year ended

December 31, 2016.

However, during the year ended

December 31, 2015,

the PIPE warrants had a dilutive impact to net loss per share due to a lower share price at

December 31, 2015,

compared to the closing share price on

December

31,

2014.

The decrease in share price created a lower Black-Scholes value and lower liability for the PIPE warrants, which resulted in other income during the year ended

December 31, 2015.

The calculation of diluted net loss per share requires that, to the extent the average market price of the underlying shares for the reporting period exceeds the exercise price of the PIPE warrants and the presumed exercise of such securities are dilutive to loss per share for the period, adjustments to net loss used in the calculation are required to remove the change in fair value of the PIPE warrants for the period. Likewise, adjustments to the denominator are required to reflect the related dilutive shares.

The following table is a reconciliation of the numerators and denominators used in the calculation of basic and diluted net loss per share computations for the years ended

December

31,

2017,

2016

and

2015:

	Years Ended December 31,
	201 7			201 6			201 5
	(in thousands, except share and per share amounts)
Numerator:
Net loss used to compute net loss per share
Basic	$	(51,508	)	$	(43,157	)	$	(24,399	)
Adjustments for change in fair value of warrant liability		—			—			(2,120	)
Diluted	$	(51,508	)	$	(43,157	)	$	(26,519	)
Denominator:
Weighted average shares outstanding used to compute net loss per share:
Basic		46,883,535			45,313,118			44,300,099
Dilutive effect of warrants		—			—			168,341
Diluted		46,883,535			45,313,118			44,468,440
Net loss per share —basic	$	(1.10	)	$	(0.95	)	$	(0.55	)
Net loss per share —diluted	$	(1.10	)	$	(0.95	)	$	(0.60	)

The following outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share of common stock for the periods presented because including them would have been antidilutive:

	Year Ended December 31,
	201 7		201 6		201 5
ESPP and stock options to purchase common stock		8,767,783		6,395,879		4,699,121
Convertible debt into common stock		—		553,763		553,763
Common stock warrants		176,730		692,611		180,155

Note 15 - Accrued Liabilities

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Accounts Payable and Accrued Liabilities Disclosure [Text Block]

15.

Accrued Liabilities

Accrued liabilities consist of the following (in thousands):

	December 31,
	201 7		201 6
Accrued compensation and employee benefits	$	2,190	$	2,556
Inventory and other contract manufacturing accruals		511		1,218
Other accrued liabilities		842		821
Total accrued liabilities	$	3,543	$	4,595

Note 16 - 401(k) Plan	12 Months Ended
Note 16 - 401(k) Plan	Dec. 31, 2017
Notes to Financial Statements
Pension and Other Postretirement Benefits Disclosure [Text Block]	16. 401 (k) Plan The Company sponsors a 401 (k) plan that stipulates that eligible employees can elect to contribute to the 401 (k) plan, subject to certain limitations. Pursuant to the 401 (k) plan, the Company makes a matching contribution of up to 4% of the related compensation. Under the vesting schedule, employees have ownership in the matching Employer Contributions based on the number of years of vesting service completed. Company contributions were $0.3 million, $0.3 million and $0.3 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Note 17 - Related Party Transactions	12 Months Ended
Note 17 - Related Party Transactions	Dec. 31, 2017
Notes to Financial Statements
Related Party Transactions Disclosure [Text Block]	17. Related Party Transaction Stephen Hoffman is a Senior Advisor to PDL and a member of the Company's Board of Directors, or the Board. The Board was aware of Dr. Hoffman ’s status as an interested party in the Royalty Monetization and Dr. Hoffman recused himself from all deliberations and actions taken by the Board with respect to the Royalty Monetization. Dr. Hoffman’s consulting compensation from PDL is composed, in part, of a success fee which is formula driven based on a minimum dollar value of deals and the total dollar value of the deals, his relative contribution to each of the concluded deals, and the total dollar value deployed in 2015. PDL estimates the amount attributable to the AcelRx transaction in the year ended December 31, 2015 to be approximately $0.3 million. The Company makes royalty payments to PDL in connection with the Royalty Monetization as described in Note 8 “Liability Related to Sale of Future Royalties.”

Note 18 - Income Taxes

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Income Tax Disclosure [Text Block]

18.

Income Taxes

The Company recorded a benefit for income taxes of

$0.7

million during the year ended

December 31, 2017,

and a benefit for income taxes of

$34.0

thousand during the year ended

December

31,

2016.

The Company recorded a provision for income taxes of

$0.8

million during the year ended

December

31,

2015.

The provision (benefit) for income taxes consisted of the following (in thousands):

	December 31, 201 7			December 31, 201 6
Current:
Federal	$	(702	)	$	(39	)
State		1			6
Total Current		(701	)		(33	)
Deferred:
Federal		—			(1	)
State		—			—
Total D eferred		—			(1	)
Provision (benefit) for income taxes	$	(701	)	$	(34	)

Net deferred tax assets as of D

ecember

31,

2017

and

2016

consist of the following (in thousands):

	December 31, 201 7			December 31, 201 6
Deferred tax assets:
Accruals and other	$	2,717		$	3,746
Research credits		6,530			5,670
Net operating loss carryforward		31,064			36,224
Section 59(e) R&D expenditures		12,156			16,782
Deferred revenue		18,384			24,836
AMT credit		—			703
Total deferred tax assets		70,851			87,961
Valuation allowance		(70,851	)		(87,961	)
Net deferred tax assets	$	—		$	—

Reconciliations of the statutory federal income tax to the Company

’s effective tax during the years ended

December

31,

2017,

2016

and

2015

are as follows (in thousands):

	Year Ended December 31,
	201 7			2016			2015
Tax at statutory federal rate	$	(17,751	)	$	(14,685	)	$	(8,037	)
State tax —net of federal benefit		350			(73	)		2,853
PIPE Warrant liability		(70	)		(260	)		(726	)
General Business credits		(316	)		(360	)		(455	)
Stock Options		42			1,115			1,559
Other		51			33			73
Change in valuation allowance		(17,110	)		14,196			5,493
Tax Reform – Tax Rate Change		34,103			—			—
Provision for income taxes	$	(701	)	$	(34	)	$	760

ASC

740

requires that the tax benefit of net operating losses, temporary differences and credit carryforwards be recorded as an asset to the extent that management assesses that realization is “more likely than

not.”

Realization of deferred tax assets is dependent on future taxable income, if any, the timing and the amount of which are uncertain. Accordingly, the deferred tax assets have been fully offset by a valuation allowance. The valuation allowance

decreased by

$17.1

million during year ended

December

31,

2017

and increased by

$14.2

million and

$5.5

million during the years ended

2016

and

2015,

respectively.

As of

December

31,

2017,

the Company had federal net operating loss carryforwards of

$115.6

million, which begin to expire in

2029.

As of

December

31,

2017,

the Company had state net operating loss carryforwards of

$97.2

million, which begin to expire in

2028.

As of

December 31, 2017,

the Company had a federal alternative minimum tax credit carryover of

$0.7

million

which is now refundable under the tax reform enacted on

December 22, 2017

and classified as a non-current receivable on the Company’s balance sheet.

As of

December

31,

2017,

the Company had federal research credit carryovers of

$5.9

million, which begin to expire in

2026.

As of

December

31,

2017,

the Company had state research credit carryovers of

$3.6

million, which will carryforward indefinitely.

The Company has adopted ASU

2016

in calendar year end

December 31, 2017.

As a result of this adoption, the Company is reflecting the excess tax benefit related to share based compensation in the current year. The impact of this adoption results in a gross increase of

$2.9

million and

$2.0

million to federal and state NOLs respectively. The Company has recorded a full valuation allowance against its deferred tax assets.

Under Section

382

of the Internal Revenue Code of

1986,

as amended, if a corporation undergoes an “ownership change,” generally defined as a greater than

50%

change (by value) in its equity ownership over a

three

year period, the corporation’s ability to use its pre-change net operating loss carryforwards and other pre-change tax attributes, such as research credits, to offset its post-change income

may

be limited. Based on an analysis performed by the Company as of

December

31,

2013,

it was determined that

two

ownership changes have occurred since inception of the Company. The

first

ownership change occurred in

2006

at the time of the Series A financing and, as a result of the change,

$1.4

million in federal and state net operating loss carryforwards will expire unutilized. In addition,

$26,000

in federal and state research and development credits will expire unutilized. The

second

ownership change occurred in

July 2013

at the time of the underwritten public offering; however, the Company believes the resulting annual imposed limitation on use of pre-change tax attributes is sufficiently high that the limit itself will

not

result in unutilized pre-change tax attributes. If it is determined that an ownership change occurred post

2013,

the Company’s tax attributes

may

be subject to limitation.

December 22, 2017,

the Tax Cuts and Jobs Act of

2017

(the “Act”) was signed into law resulting in significant changes to the Internal Revenue Code. The Act reduces the federal corporate income tax rate decrease from

35%

21%

effective for tax

periods beginning after

December 31, 2017,

changes U.S international taxation from a worldwide tax system to a territorial system, and a

one

-time transition tax on the untaxed cumulative foreign earnings and profits as of

December 31, 2017.

The Act also includes provisions for the elimination of the Alternative Minimum Tax, among other changes. The Company has calculated its best estimate of the impact of the Act in its year end income tax provision in accordance with its understanding of the Act and guidance available as of the date of this filing and as a result has recorded

$0.7

million as an additional income tax benefit in the

fourth

quarter of

2017,

the period in which the legislation was enacted. The provisional amount of

$0.7

million related to the reversal of AMT credits which are now refundable credits under the provisions of the Act. The Company has remeasured the deferred tax assets and liabilities based on the rate at which they are expected to reverse in the future.

provision or benefit has been recorded as the Company has recorded a full valuation allowance against its deferred tax assets. The effects of other provisions of the Act are

not

expected to have a material impact on the Company’s financial statements.

Uncertain Tax Positions

A reconciliation of the beginning and ending balances of the unrecognized tax benefits during t

he years ended

December

31,

2017,

2016

and

2015

is as follows (in thousands):

	Year Ended December 31,
	2017		2016		2015
Unrecognized benefit —beginning of period	$	2,162	$	1,939	$	1,667
Gross decreases —prior period tax positions		—		—		—
Gross increases —current period tax positions		203		223		272
Unrecognized benefit —end of period	$	2,365	$	2,162	$	1,939

The entire amount of the unrecognized tax benefits would

not

impact the Company

’s effective tax rate if recognized.

Accrued interest and penalties related to unrecognized tax benefits are classified as income tax expense and were immaterial. The Company files income tax returns in the United States and in California.

The tax years

2005

through

2017

remain open in both jurisdictions. The Company is

not

currently under examination by income tax authorities in federal, state or other foreign jurisdictions. The Company does

not

anticipate any significant changes within

months of this reporting date of its uncertain tax positions.

Note 19 - Unaudited Quarterly Financial Data

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Quarterly Financial Information [Text Block]

. Unaudited Quarterly Financial Data

(in thousands, except per share amounts)

The following table sets forth certain unaudited quarterly financial data for the

eight

quarters ended

December

31,

2017.

The unaudited information set forth below has been prepared on the same basis as the audited information and includes all adjustments necessary to present fairly the information set forth herein. The operating results for any quarter are

not

indicative of results for any future period. All data is in thousands except per share data.

	201 7												201 6
	Q1			Q2			Q3			Q4			Q1			Q2			Q3			Q4
Revenues	$	3,109		$	2,659		$	1,487		$	740		$	3,025		$	4,531		$	3,366		$	6,435
Operating costs and expenses	$	15,182		$	12,600		$	10,348		$	8,547		$	11,547		$	12,853		$	11,341		$	13,573
Net income / (loss)	$	(15,551	)	$	(13,059	)	$	(13,013	)	$	(9,885	)	$	(10,981	)	$	(11,092	)	$	(11,402	)	$	( 9,682	)
Net income / (loss) per share (basic)	$	(0.34	)	$	(0.29	)	$	(0.28	)	$	(0.20	)	$	(0.24	)	$	(0.24	)	$	(0.25	)	$	(0.21	)
Net income / (loss) per share (diluted)	$	(0.34	)	$	(0.29	)	$	(0.28	)	$	(0.20	)	$	(0.25	)	$	(0.24	)	$	(0.25	)	$	(0.21	)

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Business Description of Entity [Policy Text Block]

The Company

AcelRx Pharmaceuticals, Inc., or the Company or AcelRx, was incorporated in Delaware on

July 13, 2005

as SuRx, Inc., and in

January 2006,

the Company changed its name to AcelRx Pharmaceuticals, Inc. The Company

’s operations are based in Redwood City, California.

AcelRx is a specialty pharmaceutical company focused on the development and commercialization of innovative therapies for the treatment of acute pain.

AcelRx’s lead product candidate, DSUVIA

™

(known as DZUVEO outside of the United States), and its follow-on product candidate, ZALVISO

not

to commercialize products by itself, the Company

may

DSUVIA

DSUVIA, is a

mcg sufentanil sublingual tablet in a single-dose applicator intended for the treatment of moderate-to-severe acute pain administered by a healthcare professional. DSUVIA

not

clinical program for DSUVIA and in

February 2017

October 12, 2017,

two

primary recommendations. First, while the safety database was suitable in number of patients, the collection of additional data was requested on at least

Type A post-action

meeting with the FDA on

January 26, 2018

to discuss the topics covered in the CRL and to clarify the path to move towards resubmission of the DSUVIA NDA, which the Company expects to resubmit in the

second

quarter of

2018,

following the completion of an HF study to validate the revised DFU. In

March 2017,

the European Medicines Agency, or EMA, notified the Company that the DZUVEO (sufentanil sublingual tablet,

mcg) Marketing Authorisation Application, or MAA, has passed validation, and that the scientific review of the MAA is underway. The MAA for DZUVEO (formerly known as ARX-

first

half of

2018

ZALVISO

ZALVISO delivers

mcg sufentanil sublingually through a non-invasive delivery route via a pre-programmed, patient-controlled analgesia, or PCA, system. ZALVISO is approved in the EEA, Norway, Iceland and

Liechtenstein and is in late-stage development in the U.S. The Company had initially submitted to the FDA an NDA seeking approval for ZALVISO in

September 2013

but received a CRL on

July 25, 2014.

Subsequently, the FDA requested an additional clinical study,

IAP312,

designed to evaluate the effectiveness of changes made to the functionality and usability of the ZALVISO device and to take into account comments from the FDA on the study protocol. In the

IAP312

study, for which top-line results were announced in

August 2017,

ZALVISO met safety, satisfaction and device usability expectations. These results will supplement the

three

Phase

trials already completed in the ZALVISO NDA resubmission. The Company plans to resubmit the NDA for ZALVISO in the

second

half of

2018.

December 16, 2013,

AcelRx and Grü

nenthal GmbH, or Grünenthal, entered into a Collaboration and License Agreement, or the License Agreement, which was amended effective

July 17, 2015

and

September 20, 2016,

September 2015,

EU member states as well as for the EEA, Norway, Iceland and Liechtenstein, or EEA. Also on

December 16, 2013,

July 22, 2015,

the Company entered into an amendment to the MSA, or the MSA Amendment, and together with the MSA, the Amended MSA, between the Company and Grünenthal, effective as of

July 17, 2015,

and together with the Amended License Agreement, the Amended Agreements.

Grü

nenthal has begun its commercial launch of ZALVISO in the European Union. Royalty revenues and non-cash royalty revenues from the commercial sales of ZALVISO in the EU are expected to be minimal for

2018

Basis of Accounting, Policy [Policy Text Block]

Basis of Presentation

Reclassification, Policy [Policy Text Block]

Reclassifications

Certain prior year amounts in the Consolidated Financial Statements have been reclassified to conform to the current year's presentation.

December 31, 2016

and

December 31, 2015.

Consolidation, Policy [Policy Text Block]

Principles of Consolidation

The Consolidated Financial Statements include the accounts of the Company and its wholly

owned subsidiary, ARPI LLC, which was formed in

September 2015

Grünenthal, pursuant to the Amended License Agreement, or the Royalty Monetization. All intercompany accounts and transactions have been eliminated in consolidation. Refer to Note

“Liability Related to Sale of Future Royalties” for additional information.

Use of Estimates, Policy [Policy Text Block]

Use of Estimates

not

readily apparent from other sources. Actual results could differ from those estimates.

Cash, Cash Equivalents, and Marketable Securities [Policy Text Block]

Cash, Cash Equivalents and Marketable Securities

The Company considers all highly liquid investments with an original maturity (at date of purchase) of

three

months or less to be cash equivalents. Cash and cash equivalents consist of cash on deposit with banks.

Fair Value Measurement, Policy [Policy Text Block]

Fair Value of Financial Instruments

three

-level valuation hierarchy for disclosure of fair value measurements as follows:

Level I

—Unadjusted quoted prices in active markets for identical assets or liabilities;

Level II

—Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are

not

active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and

Level III

—Unobservable inputs that are supported by little or

market activity for the related assets or liabilities.

The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.

Segment Reporting, Policy [Policy Text Block]

Segment Information

The Company operates in a single segment, the development and commercialization of product candidates for the treatment of pain. The Company

Concentration Risk, Credit Risk, Policy [Policy Text Block]

Concentration of Risk

The Company invests cash that is currently

not

The Company relies on a single

third

-party supplier for the supply of sufentanil, the active pharmaceutical ingredient in

ZALVISO, and various sole-source

third

-party contract manufacturer organizations to manufacture the ZALVISO drug cartridge and device components, including the controller, the dispenser kit and the accessories.

To date, the Company has had only

two

customers. These

two

customers account for

100%

of the revenues for the years ended

December 31,

2017,

2016

and

2015.

One of these customers accounted for

79%

of the accounts receivable balance as of

December 31, 2017,

while the other customer accounted for

71%

and

84%

of the accounts receivable balance as of

December 31, 2016

and

2015,

respectively.

The Company has

not

experienced any losses with respect to the collection of its

accounts receivable and believes that the entire accounts receivable balance as of

December 31, 2017

is collectible.

Receivables, Policy [Policy Text Block]

Accounts Receivable, Net

The Company has receivables from its collaboration partner and the U.S. Department of Defense, or DoD. To date, the Company has

not

’s assessment of the credit worthiness of its customers or any other potential circumstances that could result in bad debt.

Inventory, Policy [Policy Text Block]

Inventories

Inventories are valued at the lower of cost

and net realizable value. Cost is determined using the

first

-in,

first

-out method for all inventories. Inventory includes the cost of the active pharmaceutical ingredients, or API, raw materials and

third

Indirect overhead costs in excess of normal capacity are recorded as period costs in the period incurred.

During the year ended

December 31, 2017,

the Company recorded an inventory impairment charge of

$0.4

million, primarily for ZALVISO raw materials inventory on hand, plus related purchase commitments.

Because selling prices to Grünenthal

are set to recover only direct costs with minimal mark up, all inventories are carried at net realizable value.

Property, Plant and Equipment, Policy [Policy Text Block]

Property and Equipment

three

five

years. Leasehold improvements are amortized over the shorter of the estimated useful life of the improvements or the remaining lease term.

Expenditures for repairs and maintenance, which do

not

Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]

Impairment of Long-Lived Assets

not

receive regulatory approval for its other product candidates, the Company

may

determine that it is

September 30, 2015,

$0.5

million in the year ended

December 31, 2015,

which was recorded in interest income and other income (expense), net in the Consolidated Statements of Comprehensive Loss. As of

December

31,

2017,

the Company has

not

written down any additional long-lived assets as a result of impairment.

Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]

Restricted Cash

Under the Company

Debt, Policy [Policy Text Block]

Debt Issuance Costs

Debt issuance costs, which are included in long-term debt, net of current portion, are amortized as interest expense over the contractual terms of the related credit facilities.

Contingent Put Option, Policy [Policy Text Block]

Contingent put option

The contingent put option associated with the Company

“Long-Term Debt”.

Warrants, Policy [Policy Text Block]

Warrants

Warrants issued in connection with the Company

’s Private Placement, completed in

June 2012,

are recorded as liabilities as they have the potential for cash settlement upon the occurrence of certain transactions (as defined in the warrant; see Note

“Warrants”). Changes in the fair value of the warrants are recognized as interest income and other income (expense), net in the Consolidated Statements of Comprehensive Loss.

Revenue Recognition, Policy [Policy Text Block]

Revenue Recognition

Collaboration Revenue

Collaboration revenue, which is earned under license agreements with

third

parties,

may

include nonrefundable license fees, cost reimbursements, research and development services, commercial manufacturing services, contingent development and commercial milestones and royalties.

AcelRx accounts for multiple-element arrangements in accordance with ASC Topic

605

25,

Revenue Recognition—Multiple-Element Arrangements

, or ASC

605

25.

not

meet these criteria are combined and accounted for as a single unit of accounting.

vendor-specific objective evidence, or

VSOE, of selling price or

third

-party evidence, or

TPE, of selling price. If neither exists the Company uses best estimated selling price, or

BESP, for that deliverable. Revenue allocated is then recognized when the

four

basic revenue recognition criteria are met for each element.

VSOE is based on the price charged when the element is sold separately and is the price actually charged for that deliverable. Establishing VSOE

may

not

’s price for similar deliverables when sold separately. AcelRx

may

not

The process for determining BESPs involves management

’s judgment. AcelRx’ process considers multiple factors such as discounted cash flows, estimated direct expenses and other costs and available data, which

may

vary over time, depending upon the circumstances, and relate to each deliverable. If the estimated obligation period of

one

or more deliverables should change, the future amortization of the revenue would also change.

Contract and Other Revenue

May 2015,

the Company entered into the DoD Contract with the USAMRMC to support the development of

may

increase or decrease based on actual expenses incurred.

Cost of Sales, Policy [Policy Text Block]

Cost of Goods Sold

Under the Amended Agreements with Grünenthal, the Company will sell

ZALVISO to Grünenthal at direct cost with minimal markup and will recognize indirect costs as period costs where they are in excess of normal capacity and

not

realizable on a lower of cost or market basis. Cost of goods sold for ZALVISO shipped to Grünenthal includes the inventory costs of API,

third

-party contract manufacturing costs, packaging and distribution costs, shipping, handling and storage costs, depreciation and costs of the employees involved with production.

Research and Development Expense, Policy [Policy Text Block]

Research and Development Expenses

Share-based Compensation, Option and Incentive Plans, Director Policy [Policy Text Block]

Stock-Based Compensation

Compensation expense for all share-based payment awards made to employees and directors, including employee stock options

and restricted stock units related to the

2011

Equity Incentive Plan, or

2011

EIP, and employee share purchases related to the

2011

during the years ended

December 31, 2016

and

2015,

were primarily determined using the simplified method in accordance with guidance provided by the SEC. Such method was utilized as the Company did

not

December 31, 2017,

December 31, 2016

and

2015,

the Company estimated forfeitures at the time of grant and revised those estimates in subsequent periods if actual forfeitures differed from those estimates. Effective

January 1, 2017,

the Company adopted ASU

2016

and elected to recognize forfeitures when they occur using a modified retrospective approach, which did

not

have a material impact on its Consolidated Financial Statements.

Costs Associated with Exit or Disposal Activities or Restructurings, Policy [Policy Text Block]

Restructuring Costs

Interest Expense, Policy [Policy Text Block]

Non-Cash Interest Expense on Liability Related to Sale of Future Royalties

September 2015,

the Company

December 16, 2013,

as amended, to PDL for an upfront cash purchase price of

$65.0

and milestone payments to be received by PDL and payments the Company is required to make to PDL, up to a capped amount of

$195.0

million, over the life of the arrangement. The sum of the capped amount of

$195.0

million, less the

$61.2

14%.

The Company

will record non-cash royalty revenues and non-cash interest expense within its Consolidated Statements of Comprehensive Loss over the term of the PDL agreement.

Comprehensive Income, Policy [Policy Text Block]

Comprehensive Loss

’s investments.

Income Tax, Policy [Policy Text Block]

Income Taxes

not.

Earnings Per Share, Policy [Policy Text Block]

Net Loss per Share of Common Stock

The Company

“Net Loss per Share of Common Stock”.

New Accounting Pronouncements, Policy [Policy Text Block]

Recently

Adopted Accounting Pronouncement

March 2016,

the FASB issued ASU

No.

2016

09,

Compensation - Stock Compensation (Topic

718

)

December 15, 2016,

with early adoption permitted. Under this guidance, on a prospective basis, companies will

January 1, 2017,

not

result in a net impact to retained earnings, and elected to recognize forfeitures when they occur using a modified retrospective approach, which did

not

have a material impact on its Consolidated Financial Statements.

July 2015,

the FASB issued ASU

No.

2015

11,

Inventory (Topic

330

) Related to Simplifying the Measurement of Inventory,

which applies to all inventory measured using

first

-in,

first

No.

2015

was adopted by the Company beginning in fiscal

2017,

and did

not

have a material impact on its Consolidated Financial Statements.

Recently Issued

Accounting Pronouncements

May 2017,

the FASB issued ASU

2017

09,

Compensation - Stock Compensation (Topic

718

Scope of Modification Accounting

, to clarify which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting under ASC

718.

Under the new guidance, an entity will

not

apply modification accounting to a share-based payment award if all of the following remain unchanged immediately before and after the change of terms and conditions:

•

The award’s fair value (or calculated value or intrinsic value, if those measurement methods are used),

•

The award’s vesting conditions, and

•

The award’s classification as an equity or liability instrument.

ASU

2017

is effective for annual periods, and interim periods within those annual periods, beginning after

December 15, 2017

for all entities. Early adoption is permitted, including adoption in any interim period for which financial statements have

not

yet been issued or made available for issuance. The ASU will be applied prospectively to awards modified on or after the adoption date. The Company does

not

expect the adoption of ASU

2017

to have a material effect on its results of operations, financial condition or cash flows.

November 2016,

the FASB issued ASU

No.

2016

18,

Statement of Cash Flows (Topic

230

): Restricted Cash

. ASU

No.

2016

is effective retrospectively on

January 1, 2018,

with early adoption permitted. The Company does

not

expect the adoption of ASU

2016

to have a material effect on its results of operations, financial condition or cash flows.

August 2016,

the

FASB issued ASU

No.

2016

15,

Statement of Cash Flows (Topic

230

): Classification of Certain Cash Receipts and Cash Payments,

addressing

eight

specific cash flow issues in an effort to reduce diversity in practice. The amended guidance is effective for fiscal years beginning after

December 15, 2017,

and for interim periods within those years. Early adoption is permitted. The Company does

not

expect the amended guidance to have a material impact on its Consolidated Statements of Cash Flows.

February 2016,

the FASB issued ASU

No.

2016

02,

Leases (Topic

842

)

December 15, 2018,

with early adoption permitted. The Company has

not

yet selected a transition date, and is currently evaluating the impact of the adoption of this standard on its Consolidated Financial Statements.

May 2014,

the FASB issued ASU

No.

2014

09,

Revenue from Contracts with Customers

, to provide guidance on revenue recognition. ASU

No.

2014

may

August 2015,

the FASB issued ASU

No.

2015

14,

Revenue from Contracts with Customers (Topic

606

): Deferral of the Effective Date

, which provided for the adoption of the new standard for fiscal years beginning after

December 15, 2017.

Accordingly, ASU

No.

2014

is effective for the Company in the

first

quarter of

2018.

Early adoption up to the

first

quarter of

2017

was permitted. Upon adoption, ASU

No.

2014

No.

2014

and have the same effective date as the original standard:

●

ASU

No.

2016

08,

Revenue from Contracts with Customers (Topic

606

): Principal versus Agent Considerations (Reporting Revenue Gross versus Net)

;

●

ASU

No.

2016

10,

Identifying Performance Obligations and Licensing (Topic

606

);

●

ASU

No.

2016

11,

Revenue Recognition (Topic

605

) and Derivatives and Hedging (Topic

815

): Rescission of SEC Guidance Because of Accounting Standards Updates

2014

and

2014

Pursuant to Staff Announcements at the

March 3, 2016

EITF Meeting;

●

ASU

No.

2016

12,

Revenue from Contracts with Customers (Topic

606

): Narrow-Scope Improvements and Practical Expedients; and

●

ASU

No.

2016

20,

Revenue from Contracts with Customers (Topic

606

): Technical Corrections and Improvements

The Company

adopted the new standard effective

January 1, 2018

not

be material. In addition, there is

change to the units of accounting previously identified under legacy GAAP which are now considered performance obligations under the new guidance.

Note 2 - Investments and Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Cash, Cash Equivalents and Investments [Table Text Block]

	As of December 31 , 201 7
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Cash and cash equivalents:
Cash	$	29,765	$	—	$	—	$	29,765
U.S. government agency securities		23,137		—		—		23,137
Total cash and cash equivalents		52,902		—		—		52,902

Marketable securities :
U.S. government agency securities	$	7,567	$	—	$	—	$	7,567
Total marketable securities		7,567		—		—		7,567

Total cash, cash equivalents and investments	$	60,469	$	—	$	—	$	60,469

	As of December 31 , 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Cash and cash equivalents:
Cash	$	49,833	$	—	$	—	$	49,833
U.S. government agency securities		30,474		3		—		30,477
Total cash and cash equivalents		80,307		3		—		80,310
Total cash, cash equivalents and investments	$	80,307	$	3	$	—	$	80,310

Fair Value Measurements, Recurring and Nonrecurring [Table Text Block]

	As of December 31 , 201 7
	Fair Value		Level I		Level II		Level III
Assets
U.S. government agency obligations	$	30,704	$	—	$	30,704	$	—
Total assets measured at fair value	$	30,704	$	—	$	30,704	$	—

Liabilities
Contingent put option liability	$	207	$	—	$	—	$	207
Total liabilities measured at fair value	$	207	$	—	$	—	$	207

	As of December 31 , 2016
	Fair Value		Level I		Level II		Level III
Assets
U.S. government agency obligations	$	30,477	$	—	$	30,477	$	—
Total assets measured at fair value	$	30,477	$	—	$	30,477	$	—

Liabilities
PIPE warrants	$	288		—		—	$	288
Contingent put option liability		124		—		—		124
Total liabilities measured at fair value	$	412	$	—	$	—	$	412

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

	Year Ended December 31, 201 7
Fair value —beginning of period	$	412
Expiration of fair value of PIPE warrants		(288	)
Change in fair value of contingent put option associated with Original Loan Agreement		83
Fair value —end of period	$	207

	Year Ended December 31, 201 6
Fair value —beginning of period	$	1,179
Change in fair value of PIPE warrants		(625	)
Change in fair value of contingent put option associated with Original Loan Agreement		(142	)
Fair value —end of period	$	412

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Note 3 - Inventories (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Schedule of Inventory, Current [Table Text Block]

	As of December 31,
	201 7		201 6
Raw materials	$	702	$	1,126
Work-in-process		254		296
Finished goods		—		732
Inventories	$	956	$	2,154

Note 4 - Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Property, Plant and Equipment [Table Text Block]

	As of December 31,
	201 7			201 6
Laboratory equipment	$	3,920		$	3,775
Leasehold improvements		4,469			4,469
Computer equipment and software		241			266
Construction in process		9,703			7,816
Tooling		1,109			1,074
Furniture and fixtures		47			48
		19,489			17,448
Less accumulated depreciation and amortization		(8,438	)		(6,736	)
Property and equipment, net	$	11,051		$	10,712

Note 6 - Collaboration Agreement (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Revenue Recognition Amended Agreements [Table Text Block]

	Years Ended December 31,
	201 7		201 6		2015
License	$	—	$	—	$	13,167
Product sales		6,673		5,742		—
Joint steering committee, research and development services and demonstration devices		269		688		1,690
Non-cash royalty revenue related to Royalty Monetization (See Note 8)		151		7		—
Royalty revenue		50		3		—
Total	$	7,143	$	6,440	$	14,857

Note 7 - Long-term Debt (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Schedule of Maturities of Long-term Debt [Table Text Block]

20 18	$	9,350
2019		9,350
20 20		3,704
Total payments		22,404
Less amount representing interest		(2,420	)
Notes payable, gross		19,984
Unamortized portion of final payment		(741	)
Unamortized discount on notes payable		(147	)
Long-term debt		19,096
Less current portion of notes payable, including unamortized discount		(7,727	)
Long-term debt, current portion	$	11,369

Note 8 - Liability Related to Sale of Future Royalties (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Other Liabilities [Table Text Block]

	Year ended December 31, 201 7			Period from inception to December 31, 201 7
Liability related to sale of future royalties — beginning balance	$	72,987		$	—
Proceeds from sale of future royalties		—			61,184
Non-cash royalty revenue		(120	)		(127	)
Non-cash interest expense recognized		10,721			22,531

Liability related to sale of future royalties as of December 31, 2017		83,588			83,588
Less: current portion		(604	)		(604	)
Liability related to sale of future royalties — net of current portion	$	82,984		$	82,984

Note 10 - Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]

Year Ending December 31:
201 8	$	959
2019		1,231
2020		1,268
2021		1,305
2022		1,345
Thereafter		1,501
Total minimum payments	$	7,609

Note 12 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	December 31, 201 7		December 31, 201 6		December 31, 201 5
Cost of goods sold	$	324	$	302	$	67
Research and development		1,901		2,308		2,587
General and administrative		2,069		1,869		2,356
Total	$	4,294	$	4,479	$	5,010

Share-based Compensation, Stock Options, Activity [Table Text Block]

	Number of Stock Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
								(in thousands)
December 31, 2016		6,307,756		$	5.00
Granted		3,007,155			2.99
Forfeited		(438,519	)		4.28
Expired		(351,922	)		7.31
Exercised		(69,372	)		1.52
December 31, 2017		8,455,098		$	4.25		7.1	$	13
Vested and exercisable options —December 31, 2017		4,529,174		$	5.11		5.56	$	13
Vested and expected to vest —December 31, 2017		8,455,098		$	4.25		7.1	$	13

Schedule of Share-based Compensation, Stock Options Outstanding and Exercisable Activity [Table Text Block]

			Options Outstanding						Options Vested and Exercisable
Exercise Prices			Number of Stock Options Outstanding		Weighted-Average Remaining Contractual Life (Years)		Weighted-Average Exercise Price per Share		Shares Subject to Stock Options		Weighted-Average Exercise Price per Share
$1.20	-	$2. 30		105,900		8.4	$	2.13		38,400	$	1.84
$2. 40	-	$3.77		5,592,633		7.7	$	3.10		1,948,300	$	3.17
$ 3.92	-	$6.60		2,060,565		5.7	$	5.45		1,880,190	$	5.36
$8.18	-	$10.55		696,000		6.2	$	10.28		662,284	$	10.28
				8,455,098		7.1	$	4.25		4,529,174	$	5.11

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Year Ended December 31,
	201 7			201 6			201 5
Expected term (in years)	5.70			5.25	-	6.25	5.25	-	6.25
Risk-free interest rate	1.82%	-	2.09%	1.24%	-	1.47%	1.35%	-	1.82%
Expected volatility	73%			80%			72%
Expected dividend rate	0%			0%			0%

Note 14 - Net Loss Per Share of Common Stock (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]

	Years Ended December 31,
	201 7			201 6			201 5
	(in thousands, except share and per share amounts)
Numerator:
Net loss used to compute net loss per share
Basic	$	(51,508	)	$	(43,157	)	$	(24,399	)
Adjustments for change in fair value of warrant liability		—			—			(2,120	)
Diluted	$	(51,508	)	$	(43,157	)	$	(26,519	)
Denominator:
Weighted average shares outstanding used to compute net loss per share:
Basic		46,883,535			45,313,118			44,300,099
Dilutive effect of warrants		—			—			168,341
Diluted		46,883,535			45,313,118			44,468,440
Net loss per share —basic	$	(1.10	)	$	(0.95	)	$	(0.55	)
Net loss per share —diluted	$	(1.10	)	$	(0.95	)	$	(0.60	)

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

	Year Ended December 31,
	201 7		201 6		201 5
ESPP and stock options to purchase common stock		8,767,783		6,395,879		4,699,121
Convertible debt into common stock		—		553,763		553,763
Common stock warrants		176,730		692,611		180,155

Note 15 - Accrued Liabilities (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Schedule of Accrued Liabilities [Table Text Block]

	December 31,
	201 7		201 6
Accrued compensation and employee benefits	$	2,190	$	2,556
Inventory and other contract manufacturing accruals		511		1,218
Other accrued liabilities		842		821
Total accrued liabilities	$	3,543	$	4,595

Note 18 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

	December 31, 201 7			December 31, 201 6
Current:
Federal	$	(702	)	$	(39	)
State		1			6
Total Current		(701	)		(33	)
Deferred:
Federal		—			(1	)
State		—			—
Total D eferred		—			(1	)
Provision (benefit) for income taxes	$	(701	)	$	(34	)

Schedule of Deferred Tax Assets [Table Text Block]

	December 31, 201 7			December 31, 201 6
Deferred tax assets:
Accruals and other	$	2,717		$	3,746
Research credits		6,530			5,670
Net operating loss carryforward		31,064			36,224
Section 59(e) R&D expenditures		12,156			16,782
Deferred revenue		18,384			24,836
AMT credit		—			703
Total deferred tax assets		70,851			87,961
Valuation allowance		(70,851	)		(87,961	)
Net deferred tax assets	$	—		$	—

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

	Year Ended December 31,
	201 7			2016			2015
Tax at statutory federal rate	$	(17,751	)	$	(14,685	)	$	(8,037	)
State tax —net of federal benefit		350			(73	)		2,853
PIPE Warrant liability		(70	)		(260	)		(726	)
General Business credits		(316	)		(360	)		(455	)
Stock Options		42			1,115			1,559
Other		51			33			73
Change in valuation allowance		(17,110	)		14,196			5,493
Tax Reform – Tax Rate Change		34,103			—			—
Provision for income taxes	$	(701	)	$	(34	)	$	760

Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]

	Year Ended December 31,
	2017		2016		2015
Unrecognized benefit —beginning of period	$	2,162	$	1,939	$	1,667
Gross decreases —prior period tax positions		—		—		—
Gross increases —current period tax positions		203		223		272
Unrecognized benefit —end of period	$	2,365	$	2,162	$	1,939

Note 19 - Unaudited Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Quarterly Financial Information [Table Text Block]

	201 7												201 6
	Q1			Q2			Q3			Q4			Q1			Q2			Q3			Q4
Revenues	$	3,109		$	2,659		$	1,487		$	740		$	3,025		$	4,531		$	3,366		$	6,435
Operating costs and expenses	$	15,182		$	12,600		$	10,348		$	8,547		$	11,547		$	12,853		$	11,341		$	13,573
Net income / (loss)	$	(15,551	)	$	(13,059	)	$	(13,013	)	$	(9,885	)	$	(10,981	)	$	(11,092	)	$	(11,402	)	$	( 9,682	)
Net income / (loss) per share (basic)	$	(0.34	)	$	(0.29	)	$	(0.28	)	$	(0.20	)	$	(0.24	)	$	(0.24	)	$	(0.25	)	$	(0.21	)
Net income / (loss) per share (diluted)	$	(0.34	)	$	(0.29	)	$	(0.28	)	$	(0.20	)	$	(0.25	)	$	(0.24	)	$	(0.25	)	$	(0.21	)

Note 1 - Organization and Summary of Significant Accounting Policies (Details Textual) $ in Thousands		1 Months Ended	12 Months Ended			27 Months Ended
	Sep. 18, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($)
Inventory Write-down			$ 369
Proceeds From Sale of Royalty and Milestone Rights	$ 65,000	$ 65,000
Royalty Arrangment Maximum Payments	$ 195,000	195,000
Net Proceeds from Sale of Future Royalties		$ 61,200			61,184	$ 61,184
Effective Annual Interest Rate	14.00%	14.00%
Interest Income [Member]
Asset Impairment Charges			$ 0		$ 500
Minimum [Member]
Property, Plant and Equipment, Useful Life			3 years
Maximum [Member]
Property, Plant and Equipment, Useful Life			5 years
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member]
Number of Major Customers			2	2	2
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member] \| Two Customers [Member]
Concentration Risk, Percentage			100.00%	100.00%	100.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| One Customer [Member]
Concentration Risk, Percentage			79.00%	71.00%	84.00%

Note 2 - Investments and Fair Value Measurement (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Gross, Unrealized Gain (Loss) Accumulated In Investments	$ 0	$ 0
Available-for-sale Securities, Gross Realized Gain (Loss)	0	0
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	0	0
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	$ 0	$ 0

Note 2 - Investments and Fair Value Measurement - Summary of Cash, Cash Equivalents and Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Amortized Cost	$ 60,469	$ 80,307
Gross Unrealized Gains		3
Gross Unrealized Losses
Fair Value	60,469	80,310
Cash and cash equivalents:
Amortized Cost	60,469	80,307
Gross Unrealized Gains		3
Gross Unrealized Losses
Fair Value	60,469	80,310
Cash and Cash Equivalents [Member]
Amortized Cost	52,902	80,307
Gross Unrealized Gains		3
Gross Unrealized Losses
Fair Value	52,902	80,310
Cash and cash equivalents:
Amortized Cost	52,902	80,307
Gross Unrealized Gains		3
Gross Unrealized Losses
Fair Value	52,902	80,310
Cash and Cash Equivalents [Member] \| Cash [Member]
Amortized Cost	29,765	49,833
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	29,765	49,833
Cash and cash equivalents:
Amortized Cost	29,765	49,833
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	29,765	49,833
Cash and Cash Equivalents [Member] \| U.S. Government Agency Securities [Member]
Amortized Cost	23,137	30,474
Gross Unrealized Gains		3
Gross Unrealized Losses
Fair Value	23,137	30,477
Cash and cash equivalents:
Amortized Cost	23,137	30,474
Gross Unrealized Gains		3
Gross Unrealized Losses
Fair Value	23,137	$ 30,477
Marketable Securities [Member]
Amortized Cost	7,567
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	7,567
Cash and cash equivalents:
Amortized Cost	7,567
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	7,567
Marketable Securities [Member] \| U.S. Government Agency Securities [Member]
Amortized Cost	7,567
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	7,567
Cash and cash equivalents:
Amortized Cost	7,567
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	$ 7,567

Note 2 - Investments and Fair Value Measurement - Fair Value of Financial Assets and Liabilities by Level Within Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets, fair value	$ 30,704	$ 30,477
Liabilities, fair value	207	412
Contingent Put Option Liability [Member]
Liabilities, fair value	207	124
PIPE Warrants [Member]
Liabilities, fair value		288
Fair Value, Inputs, Level 1 [Member]
Assets, fair value
Liabilities, fair value
Fair Value, Inputs, Level 1 [Member] \| Contingent Put Option Liability [Member]
Liabilities, fair value
Fair Value, Inputs, Level 1 [Member] \| PIPE Warrants [Member]
Liabilities, fair value
Fair Value, Inputs, Level 2 [Member]
Assets, fair value	30,704	30,477
Liabilities, fair value
Fair Value, Inputs, Level 2 [Member] \| Contingent Put Option Liability [Member]
Liabilities, fair value
Fair Value, Inputs, Level 2 [Member] \| PIPE Warrants [Member]
Liabilities, fair value
Fair Value, Inputs, Level 3 [Member]
Assets, fair value
Liabilities, fair value	207	412
Fair Value, Inputs, Level 3 [Member] \| Contingent Put Option Liability [Member]
Liabilities, fair value	207	124
Fair Value, Inputs, Level 3 [Member] \| PIPE Warrants [Member]
Liabilities, fair value		288
U.S. Government Agency Obligations [Member]
Assets, fair value	30,704	30,477
U.S. Government Agency Obligations [Member] \| Fair Value, Inputs, Level 1 [Member]
Assets, fair value
U.S. Government Agency Obligations [Member] \| Fair Value, Inputs, Level 2 [Member]
Assets, fair value	30,704	30,477
U.S. Government Agency Obligations [Member] \| Fair Value, Inputs, Level 3 [Member]
Assets, fair value

Note 2 - Investments and Fair Value Measurement - Summary of Changes in Fair Value of Level III Financial Liabilities (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair value—beginning of period	$ 412	$ 1,179
Fair value—end of period	207	412
PIPE Warrants [Member]
Expiration of fair value of PIPE warrants	(288)	(625)
Contingent Put Option Liability [Member]
Expiration of fair value of PIPE warrants	$ 83	$ (142)

Note 3 - Inventories (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Inventory Write-down	$ 369
ZALVISO [Member]
Inventory Write-down	$ 400

Note 3 - Inventories - Inventory Components (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Raw materials	$ 702	$ 1,126
Work-in-process	254	296
Finished goods		732
Inventories	$ 956	$ 2,154

Note 4 - Property and Equipment (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Depreciation	$ 1,700	$ 2,100	$ 2,000
Property, Plant and Equipment, Gross	19,489	17,448
Construction in Progress [Member]
Property, Plant and Equipment, Gross	9,703	7,816
Construction in Progress [Member] \| Patheon Cincinnati Facility [Member]
Property, Plant and Equipment, Gross	$ 300	$ 1,500

Note 4 - Property and Equipment - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property and Equipment, Gross	$ 19,489	$ 17,448
Less accumulated depreciation and amortization	(8,438)	(6,736)
Property and equipment, net	11,051	10,712
Laboratory Equipment [Member]
Property and Equipment, Gross	3,920	3,775
Leasehold Improvements [Member]
Property and Equipment, Gross	4,469	4,469
Computer Equipment and Software [Member]
Property and Equipment, Gross	241	266
Construction in Progress [Member]
Property and Equipment, Gross	9,703	7,816
Tooling [Member]
Property and Equipment, Gross	1,109	1,074
Furniture and Fixtures [Member]
Property and Equipment, Gross	$ 47	$ 48

Note 5 - U.S. Department of Defense Contract (Details Textual) - USD ($) $ in Thousands			12 Months Ended
	Mar. 09, 2017	Mar. 02, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 28, 2018	May 11, 2015
Government Contract Receivable							$ 17,000
Contracts Revenue			$ 852	$ 10,917	$ 4,406
Subsequent Event [Member] \| Amendment to DoD Contract Incorporate Additional Services [Member]
Government Contract Receivable						$ 500
Government [Member]
Award Contract Renewal Term	330 days	120 days
Government [Member] \| Contract and Other Revenue [Member]
Contracts Revenue			$ 900	$ 10,900	$ 4,400

Note 6 - Collaboration Agreement (Details Textual) - USD ($) $ in Thousands		1 Months Ended				3 Months Ended	9 Months Ended	19 Months Ended
	Jul. 17, 2015	Feb. 29, 2016	Sep. 30, 2015	Jul. 31, 2014	Dec. 31, 2013	Sep. 30, 2014	Sep. 30, 2017	Jul. 17, 2015	Jul. 16, 2015	Dec. 31, 2017	Dec. 31, 2016
Payments in Exchange for Services Under Collaboration Agreement	$ 700
Amount of Binding Product Forecast Revenue	3,700
Revenue Recognition, Milestone Method, Revenue Recognized			$ 15,000		$ 30,000	$ 5,000		$ 33,300
Revenue Recognition Milestone Method Agreed, Additional Amount, Based On Efforts And Targets	$ 194,500							194,500
Manufacturing Agreement, Percentage for Five Years	100.00%
Manufacturing Agreement, Percentage, Thereafter	80.00%
Revenue Recognition Milestone Method Agreed, Additional Amount			$ 15,000
Deferred Revenue	$ 54,400							54,400	$ 1,700
Collaboration Agreement Consideration, Amount								35,000
Revenue Recognition Milestone Method Agreed, Allocated to Deliverables	15,000
Discount on Manufacturing Services		$ 4,400
Committee Participation Sercices Recognized		200
Manufacturing Services Revenues Related to Binding Forecast		2,300
Deferred Revenue, Current										$ 362	$ 362
Deferred Revenue, Noncurrent										$ 3,463	$ 3,824
AUSTRALIA
Revenue Recognition, Milestone Method, Revenue Recognized							$ 166,000
ZALVISO [Member]
Revenue Recognition, Milestone Method, Revenue Recognized	28,500
Milestone Payments Received				$ 5,000
ZALVISO [Member] \| Europe [Member]
Revenue Recognition, Milestone Method, Revenue Recognized	20,000
Based upon Net Sales Target Achievements [Member]
Increase (Decrease) in Milestone Payments Related to Net Sales Target	(5,500)
Potential Milestone Payments Related to Net Sales Target	166,000								$ 171,500
Revenue Recognition Milestone Method Agreed, Additional Amount, Based On Efforts And Targets	166,000							166,000
Based upon Successful Regulatory and Product Development Efforts [Member]
Revenue Recognition Milestone Method Agreed, Additional Amount, Based On Efforts And Targets	28,500							28,500
Research and Development and Demonstration Device Systems [Member]
Revenue Recognition Milestone Method Agreed, Additional Amount	700							700
Previously Delivered License [Member]
Revenue Recognition Milestone Method Agreed, Additional Amount	13,200							13,200
Research and Development and Committee Participation Services [Member]
Revenue Recognition Milestone Method Agreed, Additional Amount	$ 500	$ 500						$ 500

Note 6 - Collaboration Agreement - Summary of Revenue Recognized Under the Amended Agreements (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Non-cash royalty revenue related to Royalty Monetization (See Note 8)		$ 151	$ 7
Royalty revenue	$ 31
Collaboration agreement		7,143	6,440	14,857
Collaborative Arrangement [Member]
License				13,167
Revenue Recognized		269	688	1,690
Non-cash royalty revenue related to Royalty Monetization (See Note 8)		151	7
Royalty revenue		50	3
Collaboration agreement		7,143	6,440	14,857
Collaborative Arrangement [Member] \| ZALVISO [Member] \| Grunenthal [Member]
Revenue Recognized		$ 6,673	$ 5,742

Note 7 - Long-term Debt (Details Textual) $ / shares in Units, $ in Thousands				1 Months Ended		6 Months Ended	12 Months Ended
	Mar. 02, 2017 USD ($)	Sep. 18, 2015 $ / shares shares	Dec. 16, 2013 USD ($) $ / shares shares	Sep. 30, 2016 $ / shares shares	Dec. 31, 2013 $ / shares shares	Jun. 30, 2016 $ / shares	Mar. 01, 2020	Mar. 01, 2019	Mar. 01, 2018	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) shares	Oct. 01, 2017 USD ($)	Sep. 17, 2015 $ / shares	Dec. 31, 2014 USD ($)	Sep. 24, 2014 USD ($)	Jun. 16, 2014 USD ($)
Repayments of Long-term Debt										$ 3,514		$ 4,534
Common Stock Warrants Exercised \| shares												847,058
Fair Value of Contingent Put Option, Liability										207	124
Interest Expense										3,316	$ 2,770	$ 2,977
Hercules Warrants [Member]
Common Stock Warrants Exercised \| shares		176,730	176,730	176,730	176,730
Class of Warrant or Right, Exercise Price of Warrants or Rights \| $ / shares		$ 3.88	$ 6.79	$ 3.07	$ 9.67									$ 6.79
Investment Warrants, Exercise Price \| $ / shares				$ 3.07	$ 6.79	$ 3.88
Amended and Restated Loan and Security Agreement [Member]
Line of Credit Facility, Maximum Borrowing Capacity			$ 40,000
Number of Tranches for Loan and Security Agreement			3
Debt Instrument, Fair Value Disclosure															$ 24,900
Long-term Debt Maturities Balloon Payments													$ 1,700
Debt Instrument, Variable Rate Threshold	9.55%
Debt Instrument, Percentage Used to Calculate Variable Rate	3.50%
Debt Instrument, Final Payment, Percentage of Aggregate Principal Amount	6.50%
Amended and Restated Loan and Security Agreement [Member] \| Prime Rate [Member]
Debt Instrument, Interest Rate, Effective Percentage											9.55%
Amended and Restated Loan and Security Agreement [Member] \| First Tranche [Member]
Debt Instrument, Face Amount	$ 20,500		$ 15,000
Repayments of Long-term Debt			8,600
Amended and Restated Loan and Security Agreement [Member] \| Second Tranche [Member]
Debt Instrument, Face Amount																	$ 10,000
Amended and Restated Loan and Security Agreement [Member] \| Third Tranche [Member]
Line of Credit Facility, Maximum Borrowing Capacity																$ 15,000
Hercules Loan and Security Agreement [Member]
Additional Default Interest Rate	5.00%
Fair Value of Contingent Put Option, Liability			$ 32							200	$ 100
Long-term Line of Credit										19,100	21,500
Interest Expense										$ 3,300	$ 2,800	$ 3,000
Hercules Loan and Security Agreement [Member] \| Scenario, Forecast [Member]
Prepayment Charge of Term Loan Percentage							1.00%	2.00%	3.00%

Note 7 - Long-term Debt - Outstanding Future Payments of Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
2018	$ 9,350
2019	9,350
2020	3,704
Total payments	22,404
Less amount representing interest	(2,420)
Notes payable, gross	19,984
Unamortized portion of final payment	(741)
Unamortized discount on notes payable	(147)
Long-term debt	19,096
Less current portion of notes payable, including unamortized discount	(7,727)	$ (2,912)
Long-term debt, current portion	$ 11,369	$ 18,637

Note 8 - Liability Related to Sale of Future Royalties (Details Textual) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended
	Sep. 18, 2015	Sep. 30, 2015	Dec. 31, 2017
Proceeds From Sale of Royalty and Milestone Rights	$ 65,000	$ 65,000
Royalty Arrangment Maximum Payments	$ 195,000	195,000
Revenue Recognition Milestone Method Agreed, Additional Amount		$ 15,000
Effective Annual Interest Rate	14.00%	14.00%
Royalty Revenue			$ 31
First Four Commercial Milestones [Member]
Percentage of Royalties and Rights Under Agreement	20.00%
Royalties [Member]
Percentage of Royalties and Rights Under Agreement	25.00%
Remaining Commercial and All Development Milestone[Member]
Percentage of Royalties and Rights Under Agreement	100.00%
Commercial Milestones Value	$ 43,500
MAA Aproval [Member]
Revenue Recognition Milestone Method Agreed, Additional Amount	15,000
PDL [Member]
Proceeds From Sale of Royalty and Milestone Rights	$ 61,200
Percentage of Royalties and Rights Under Agreement	75.00%
PDL [Member] \| First Four Commercial Milestones [Member]
Percentage of Royalties and Rights Under Agreement	80.00%
Commercial Milestones Value Maximum Amount Available	$ 35,600
AcelRX [Member] \| First Four Commercial Milestones [Member]
Commercial Milestones Value Maximum Amount Available	$ 44,500

Note 8 - Liability Related to Sale of Future Royalties - Activity of Liability Related to Sale of Future Royalties (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended			27 Months Ended
	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Liability related to sale of future royalties — beginning balance		$ 72,987
Proceeds from sale of future royalties	$ 61,200			$ 61,184	61,184
Non-cash royalty revenue		(120)			(127)
Non-cash interest expense recognized		10,721	9,382	$ 2,428	22,531
Liability related to sale of future royalties as of December 31, 2017		83,588	72,987		83,588
Less: current portion		(604)	(764)		(604)
Liability related to sale of future royalties — net of current portion		$ 82,984	$ 72,223		$ 82,984

Note 9 - Warrants (Details Textual) $ / shares in Units, $ in Thousands			1 Months Ended			6 Months Ended	12 Months Ended
	Sep. 18, 2015 $ / shares shares	Dec. 16, 2013 $ / shares shares	Sep. 30, 2016 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares $ / item shares	Jun. 30, 2012 USD ($) $ / shares shares	Jun. 30, 2016 $ / shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) shares	Sep. 30, 2015 USD ($)	Sep. 17, 2015 $ / shares
Common Stock Warrants Exercised									847,058
Stock Issued During Period, Shares, Common Stock Warrants Exercised									527,101
2012 Private Placement [Member]
Fair Value of Warrant Upon Execution of Securities Purchase Agreement \| $					$ 5,800
Other Expenses \| $							$ 300	$ 600	$ 2,100
Hercules Warrants [Member]
Common Stock Warrants Exercised	176,730	176,730	176,730	176,730
Investment Warrants, Exercise Price \| $ / shares			$ 3.07	$ 6.79		$ 3.88
Class of Warrant or Right, Exercise Price of Warrants or Rights \| $ / shares	$ 3.88	$ 6.79	$ 3.07	$ 9.67							$ 6.79
Warrant Exercisable Term				5 years
Fair Value of Warrant On Date Of Issuance \| $			$ 45	$ 1,100						$ 100
Derivative, Price Risk Option Strike Price \| $ / item				6.79
Class of Warrant or Right Fair Value Assumption Risk Free Interest Rate				1.55%
Class of Warrant or Right Fair Value Assumption Stock Volatility				71.00%
Class of Warrant or Right Fair Value Assumption Expected Dividend Yield				0.00%
Class of Warrant or Right, Outstanding							176,730
PIPE Warrants [Member]
Investment Warrants, Exercise Price \| $ / shares					$ 3.40
Warrant Exercisable Term					5 years
Class of Warrant or Right, Outstanding					2,630,103		512,456
Warrants Vesting Condition Description					50.00%

Note 10 - Commitments and Contingencies (Details Textual) $ in Thousands			1 Months Ended	12 Months Ended
	Jun. 14, 2017 USD ($) a	Oct. 02, 2015 ft² $ / item	May 31, 2014 ft²	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2011 ft²
Rental Rate Per Square Foot \| $ / item		2.05
Future Minimum Sublease Rentals, Sale Leaseback Transactions, Next Twelve Months				$ 300
Future Minimum Sublease Rentals, Sale Leaseback Transactions, within Two Years				25
Operating Leases, Rent Expense, Net				$ 600	$ 300	$ 600
Redwood City, California [Member]
Area of Operating Lease \| ft²		11,871					13,787
Lessee, Operating Lease, Term of Contract		2 years 60 days
Lease Extended Term [Member]
Area of Operating Lease \| ft²			12,106
Lessee, Operating Lease, Renewal Term			1 year 261 days
Lease Agreement, Term			3 years 180 days
Executive Offices in Redwood City, CA [Member] \| Metropolitan Life Insurance Company [Member]
Lessee, Operating Lease, Renewal Term	6 years
Area of Real Estate Property \| a	25,893
Operating Lease, Annual Rent	$ 1,200
Lessee, Operating Lease, Term for Annual Rent Increase	1 year

Note 10 - Commitments and Contingencies - Future Minimum Payments Under Lease Agreement (Details) $ in Thousands	Dec. 31, 2017 USD ($)
2018	$ 959
2019	1,231
2020	1,268
2021	1,305
2022	1,345
Thereafter	1,501
Total minimum payments	$ 7,609

Note 11 - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Millions			1 Months Ended			12 Months Ended
	Jun. 21, 2013	Feb. 10, 2011	Nov. 30, 2009	Feb. 29, 2008	Aug. 31, 2006	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2011
Stock Issued During Period, Shares, New Issues						5,400,000
Proceeds from Issuance of Common Stock, Net						$ 15.7
Payments of Stock Issuance Costs						$ 0.5
Employee Stock Purchase Plan, Shares Issued, Weighted Average Fair Value						$ 2.59	$ 2.98	$ 4.48
2006 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized					342,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized			1,400,000	375,000
2006 Equity Incentive Plan [Member] \| Maximum [Member]
Common Stock Voting Rights Percentage					10.00%
Fair Value of Common Stock as Percentage of Option Exercise Price					110.00%
2011 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized									1,800,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other Than Options, Outstanding		52,000							1,900,000
Stock Option Plan Option Reserve Annual Increase as Percentage of Outstanding Shares Allowed									4.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period									4 years
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant						2,368,992
2011 Equity Incentive Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period									10 years
Employee Stock Purchase Plan (ESPP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized						250,000
Share-based Payment Award, Number of Shares Authorized						2.00%
Stock Issued During Period, Shares, Employee Stock Purchase Plans						94,893
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant						1,041,249
Public Offering [Member]
Proceeds from Issuance Initial Public Offering	$ 40.0

Note 12 - Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 1.91	$ 2.24	$ 2.69
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized		$ 7,100
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition		2 years 219 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value		$ 3,500	$ 3,900	$ 5,400
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value		$ 40	$ 0	$ 1,300
2011 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		2,368,992
2011 Equity Incentive Plan [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	2,035,966

Note 12 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock-based compensation expense	$ 4,294	$ 4,479	$ 5,010
Cost of Sales [Member]
Stock-based compensation expense	324	302	67
Research and Development Expense [Member]
Stock-based compensation expense	1,901	2,308	2,587
General and Administrative Expense [Member]
Stock-based compensation expense	$ 2,069	$ 1,869	$ 2,356

Note 12 - Stock-based Compensation - Option Activity (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Outstanding (in shares) \| shares	6,307,756
Outstanding (in dollars per share) \| $ / shares	$ 5
Granted (in shares) \| shares	3,007,155
Granted, weighted-average exercise price (in dollars per share) \| $ / shares	$ 2.99
Forfeited (in shares) \| shares	(438,519)
Forfeited, weighted-average exercise price (in dollars per share) \| $ / shares	$ 4.28
Expired (in shares) \| shares	(351,922)
Expired, weighted-average exercise price (in dollars per share) \| $ / shares	$ 7.31
Exercised (in shares) \| shares	(69,372)
Exercised, weighted-average exercise price (in dollars per share) \| $ / shares	$ 1.52
Outstanding (in shares) \| shares	8,455,098
Outstanding, weighted-average exercise price (in dollars per share) \| $ / shares	$ 4.25
Outstanding, weighted-average remaining contractual life (Year)	7 years 36 days
Outstanding, aggregate intrinsic value \| $	$ 13
Vested and exercisable options (in shares) \| shares	4,529,174
Vested and exercisable options, weighted-average exercise price (in dollars per share) \| $ / shares	$ 5.11
Vested and exercisable options, weighted-average remaining contractual life (Year)	5 years 204 days
Vested and exercisable options, aggregate intrinsic value \| $	$ 13
Vested and expected to vest (in shares) \| shares	8,455,098
Vested and expected to vest, weighted-average exercise price (in dollars per share) \| $ / shares	$ 4.25
Vested and expected to vest, weighted-average remaining contractual life (Year)	7 years 36 days
Vested and expected to vest, aggregate intrinsic value \| $	$ 13

Note 12 - Stock-based Compensation - Stock Options Outstanding, Vested and Exercisable (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Exercise Price Range, Lower Range Limit (in dollars per share)
Exercise Price Range, Upper Range Limit (in dollars per share)
Number of Stock Options Outstanding (in shares)	8,455,098	6,307,756
Weighted-average Remaining Contractual LIfe (Year)	7 years 36 days
Options Outstanding, Weighted-average Exercise Price Per Share (in dollars per share)	$ 4.25	$ 5
Shares Subject to Stock Options (in shares)	4,529,174
Options Vested and Exercisable, Weighted-average Exercise Price Per Share (in dollars per share)	$ 5.11
Exercise Price Range 1 [Member]
Exercise Price Range, Lower Range Limit (in dollars per share)	1.20
Exercise Price Range, Upper Range Limit (in dollars per share)	$ 2.30
Number of Stock Options Outstanding (in shares)	105,900
Weighted-average Remaining Contractual LIfe (Year)	8 years 146 days
Options Outstanding, Weighted-average Exercise Price Per Share (in dollars per share)	$ 2.13
Shares Subject to Stock Options (in shares)	38,400
Options Vested and Exercisable, Weighted-average Exercise Price Per Share (in dollars per share)	$ 1.84
Exercise Price Range 2 [Member]
Exercise Price Range, Lower Range Limit (in dollars per share)	2.40
Exercise Price Range, Upper Range Limit (in dollars per share)	$ 3.77
Number of Stock Options Outstanding (in shares)	5,592,633
Weighted-average Remaining Contractual LIfe (Year)	7 years 255 days
Options Outstanding, Weighted-average Exercise Price Per Share (in dollars per share)	$ 3.10
Shares Subject to Stock Options (in shares)	1,948,300
Options Vested and Exercisable, Weighted-average Exercise Price Per Share (in dollars per share)	$ 3.17
Exercise Price Range 3 [Member]
Exercise Price Range, Lower Range Limit (in dollars per share)	3.92
Exercise Price Range, Upper Range Limit (in dollars per share)	$ 6.60
Number of Stock Options Outstanding (in shares)	2,060,565
Weighted-average Remaining Contractual LIfe (Year)	5 years 255 days
Options Outstanding, Weighted-average Exercise Price Per Share (in dollars per share)	$ 5.45
Shares Subject to Stock Options (in shares)	1,880,190
Options Vested and Exercisable, Weighted-average Exercise Price Per Share (in dollars per share)	$ 5.36
Exercise Price Range 4 [Member]
Exercise Price Range, Lower Range Limit (in dollars per share)	8.18
Exercise Price Range, Upper Range Limit (in dollars per share)	$ 10.55
Number of Stock Options Outstanding (in shares)	696,000
Weighted-average Remaining Contractual LIfe (Year)	6 years 73 days
Options Outstanding, Weighted-average Exercise Price Per Share (in dollars per share)	$ 10.28
Shares Subject to Stock Options (in shares)	662,284
Options Vested and Exercisable, Weighted-average Exercise Price Per Share (in dollars per share)	$ 10.28

Note 12 - Stock-based Compensation - Assumptions to Calculate Fair Value of Each Employee Stock Option (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Expected term (in years) (Year)	5 years 255 days
Expected volatility	73.00%	80.00%	72.00%
Expected dividend rate	0.00%	0.00%	0.00%
Minimum [Member]
Expected term (in years) (Year)	5 years 255 days	5 years 91 days	5 years 91 days
Risk-free interest rate	1.82%	1.24%	1.35%
Expected volatility	73.00%	80.00%	72.00%
Expected dividend rate	0.00%	0.00%	0.00%
Maximum [Member]
Expected term (in years) (Year)	5 years 255 days	6 years 91 days	6 years 91 days
Risk-free interest rate	2.09%	1.47%	1.82%
Expected volatility	73.00%	80.00%	72.00%
Expected dividend rate	0.00%	0.00%	0.00%

Note 13 - Restructuring Costs (Details Textual) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Restructuring and Related Cost, Number of Positions Eliminated	19
Restructuring and Related Cost, Number of Positions Eliminated, Period Percent	36.00%
Restructuring Charges				$ 756

Note 14 - Net Loss Per Share of Common Stock - Computation of Basic and Diluted Net Loss Per Share of Common (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net loss	$ (9,885)	$ (13,013)	$ (13,059)	$ (15,551)	$ (9,682)	$ (11,402)	$ (11,092)	$ (10,981)	$ (51,508)	$ (43,157)	$ (24,399)
Adjustments for change in fair value of warrant liability											(2,120)
Diluted									$ (51,508)	$ (43,157)	$ (26,519)
Shares used in computing net loss per share of common stock, basic (in shares)									46,883,535	45,313,118	44,300,099
Dilutive effect of warrants (in shares)											168,341
Diluted (in shares)									46,883,535	45,313,118	44,468,440
Net loss per share of common stock, basic (in dollars per share)	$ (0.20)	$ (0.28)	$ (0.29)	$ (0.34)	$ (0.21)	$ (0.25)	$ (0.24)	$ (0.24)	$ (1.10)	$ (0.95)	$ (0.55)
Net loss per share of common stock, diluted (in dollars per share)	$ (0.20)	$ (0.28)	$ (0.29)	$ (0.34)	$ (0.21)	$ (0.25)	$ (0.24)	$ (0.25)	$ (1.10)	$ (0.95)	$ (0.60)

Note 14 - Net Loss Per Share of Common Stock - Common Stock Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Stock Option [Member]
Antidilutive securities (in shares)	8,767,783	6,395,879	4,699,121
Convertible Debt Securities [Member]
Antidilutive securities (in shares)		553,763	553,763
Warrant [Member]
Antidilutive securities (in shares)	176,730	692,611	180,155

Note 15 - Accrued Liabilities - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued compensation and employee benefits	$ 2,190	$ 2,556
Inventory and other contract manufacturing accruals	511	1,218
Other accrued liabilities	842	821
Total accrued liabilities	$ 3,543	$ 4,595

Note 16 - 401(k) Plan (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan, Employer Discretionary Contribution Percentage	4.00%
Contributions by Employer to Postemployment Benefit Obligations	$ 0.3	$ 0.3	$ 0.3

Note 17 - Related Party Transactions (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Royalty Monetization [Member] \| Dr. Hoffman [Member]
Related Party Transaction, Amounts of Transaction	$ 0.3

Note 18 - Income Taxes (Details Textual) - USD ($)	3 Months Ended	12 Months Ended
Note 18 - Income Taxes (Details Textual) - USD ($)	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Expense (Benefit)			$ (701,000)	$ (34,000)	$ 760,000
Valuation Allowances and Reserves, Period Increase (Decrease)			(17,100,000)	14,200,000	$ 5,500,000
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax				$ 703,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			35.00%
Tax Adjustments, Settlements, and Unusual Provisions	(700,000)
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	0
Earliest Tax Year [Member]
Open Tax Year			2005
Latest Tax Year [Member]
Open Tax Year			2017
Subject to Expiration [Member]
Operating Loss Carryforwards	1,400,000		$ 1,400,000
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%
Research Tax Credit Carryforward [Member] \| Subject to Expiration [Member]
Tax Credit Carryforward, Amount	26,000		26,000
Domestic Tax Authority [Member]
Operating Loss Carryforwards	115,600,000		115,600,000
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	700,000		700,000
Domestic Tax Authority [Member] \| Accounting Standards Update 2016-09 [Member]
Operating Loss Carryforwards	2,900,000		2,900,000
Domestic Tax Authority [Member] \| Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	5,900,000		5,900,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards	97,200,000		97,200,000
State and Local Jurisdiction [Member] \| Accounting Standards Update 2016-09 [Member]
Operating Loss Carryforwards	2,000,000		2,000,000
State and Local Jurisdiction [Member] \| Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	$ 3,600,000		$ 3,600,000

Note 18 - Income Taxes - Provision (Benefit) for Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ (702,000)	$ (39,000)
State	1,000	6,000
Total Current	(701,000)	(33,000)
Deferred:
Federal		(1,000)
State
Total Deferred		(1,000)
Provision (benefit) for income taxes	$ (701,000)	$ (34,000)	$ 760,000

Note 18 - Income Taxes - Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accruals and other	$ 2,717	$ 3,746
Research credits	6,530	5,670
Net operating loss carryforward	31,064	36,224
Section 59(e) R&D expenditures	12,156	16,782
Deferred revenue	18,384	24,836
AMT credit		703
Total deferred tax assets	70,851	87,961
Valuation allowance	(70,851)	(87,961)
Net deferred tax assets		$ 0

Note 18 - Income Taxes - Reconciliation of Statutory Federal Income Tax (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Tax at statutory federal rate	$ (17,751,000)	$ (14,685,000)	$ (8,037,000)
State tax—net of federal benefit	350,000	(73,000)	2,853,000
PIPE Warrant liability	(70,000)	(260,000)	(726,000)
General Business credits	(316,000)	(360,000)	(455,000)
Stock Options	42,000	1,115,000	1,559,000
Other	51,000	33,000	73,000
Change in valuation allowance	(17,110,000)	14,196,000	5,493,000
Tax Reform – Tax Rate Change	34,103,000
Provision (benefit) for income taxes	$ (701,000)	$ (34,000)	$ 760,000

Note 18 - Income Taxes - Reconciliation of Beginning and Ending Balance of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unrecognized benefit—beginning of period	$ 2,162	$ 1,939	$ 1,667
Gross decreases—prior period tax positions
Gross increases—current period tax positions	203	223	272
Unrecognized benefit—end of period	$ 2,365	$ 2,162	$ 1,939

Note 19 - Unaudited Quarterly Financial Data - Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total revenue	$ 740	$ 1,487	$ 2,659	$ 3,109	$ 6,435	$ 3,366	$ 4,531	$ 3,025	$ 7,995	$ 17,357	$ 19,263
Total operating costs and expenses	8,547	10,348	12,600	15,182	13,573	11,341	12,853	11,547	46,677	49,314	39,217
Net income / (loss)	$ (9,885)	$ (13,013)	$ (13,059)	$ (15,551)	$ (9,682)	$ (11,402)	$ (11,092)	$ (10,981)	$ (51,508)	$ (43,157)	$ (24,399)
Net income / (loss) per share (basic) (in dollars per share)	$ (0.20)	$ (0.28)	$ (0.29)	$ (0.34)	$ (0.21)	$ (0.25)	$ (0.24)	$ (0.24)	$ (1.10)	$ (0.95)	$ (0.55)
Net income / (loss) per share (diluted) (in dollars per share)	$ (0.20)	$ (0.28)	$ (0.29)	$ (0.34)	$ (0.21)	$ (0.25)	$ (0.24)	$ (0.25)	$ (1.10)	$ (0.95)	$ (0.60)