Note 7 - Loss Per Share (Details Textual) - shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Options and Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	27,559,457	5,676,637
Convertible Debt Securities [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,303,073
Series C Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	79,246	79,246
Series D Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	35,000	0
Series E Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,484,634	0