Note J - Common Stock and Warrants (Tables)
 12 Months Ended
Dec. 31, 2016
Notes Tables  
Schedule of Authorized Shares of Common Stock Reserved for Future Issuance [Table Text Block]
   
December 31,
  
   
2016
    
2015
  
Conversion of Deerfield Convertible Notes
    
1,751,296
      
1,991,219
  
Conversion of 2021 Notes    
 5,040,914
      
 —
  
Outstanding awards under equity incentive plans
    
1,990,260
      
1,397,511
  
Outstanding common stock warrants
    
2,087,477
      
2,325,383
  
Possible future issuances under equity incentive plans
    
1,244,671
      
1,410,848
  
Total
common shares reserved for future issuance
    
12,114,618
      
7,124,961
  
Schedule of Common Stock Outstanding Roll Forward [Table Text Block]
   
Shares of
  
   
Common Stock
  
Balance at January 1, 2014    
2,381,041
  
Balance at December 31, 2014    
2,381,041
  
Issuance of common stock in connection with the IPO    
5,854,545
  
Conversion of preferred stock to common stock in connection with the IPO    
5,980,564
  
Common stock warrants exercised    
270,038
  
Common stock options exercised    
4,766
  
Balance at December 31, 2015
    
14,490,954
  
Common stock warrants exercised    
141,095
  
Common stock options exercised    
14,933
  
Balance at December 31, 2016    
14,646,982