Note 6 - Leases - Future Minimum Sublease Payments (Details) $ in Thousands	Sep. 30, 2020 USD ($)
2020 (remaining three months)	$ 148
2021	610
2022	629
2023	648
2024	54
Total future minimum sublease payments	2,089
Rent receivable	374
Prepaid Expenses and Other Current Assets [Member]
Rent receivable	91
Other Assets [Member]
Rent receivable	$ 283

Amount of sublease payments to be received by the lessee.

No definition available.

Name:	acrx_LesseeOperatingSubleasePaymentsToBeReceived
Namespace Prefix:	acrx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of sublease payments to be received by lessee in the next twelve months.

No definition available.

Name:	acrx_LesseeOperatingSubleasePaymentsToBeReceivedDueNextTwelveMonths
Namespace Prefix:	acrx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of sublease payments to be received by lessee in fourth fiscal year following latest fiscal year.

No definition available.

Name:	acrx_LesseeOperatingSubleasePaymentsToBeReceivedDueYearFour
Namespace Prefix:	acrx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of sublease payments to be received by lessee in third fiscal year following latest fiscal year.

No definition available.

Name:	acrx_LesseeOperatingSubleasePaymentsToBeReceivedDueYearThree
Namespace Prefix:	acrx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of sublease payments to be received by lessee in second fiscal year following latest fiscal year.

No definition available.

Name:	acrx_LesseeOperatingSubleasePaymentsToBeReceivedDueYearTwo
Namespace Prefix:	acrx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of sublease payments to be received by lessee in remainder of fiscal year following latest fiscal year.

No definition available.

Name:	acrx_LesseeOperatingSubleasePaymentsToBeReceivedRemainderOfFiscalYear
Namespace Prefix:	acrx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of receivables from subleases.

No definition available.

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: