Note 5 - Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property and equipment, gross	$ 1,043	$ 990
Less accumulated depreciation	(868)	(845)
Property and equipment, net	175	145
Computer Equipment and Software [Member]
Property and equipment, gross	121	119
Laboratory and Manufacturing Equipment [Member]
Property and equipment, gross	532	481
Furniture and Fixtures [Member]
Property and equipment, gross	55	55
Leasehold Improvements [Member]
Property and equipment, gross	332	332
Construction in Progress [Member]
Property and equipment, gross	$ 3	$ 3

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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