Here is a list of the 20 most-shorted drug stocks according to short interest ratio:

1. OPKO Health (AMEX: OPK)                     short ratio: 17.0
2. Neurocrine Biosciences (Nasdaq: NBIX)       short ratio: 16.3
3. Javelin Pharmaceuticals (AMEX: JAV)         short ratio: 16.1
4. InterMunne (Nasdaq: ITMN)                   short ratio: 15.1
5. Valeant Pharmaceuticals (NYSE: VRX)         short ratio: 12.8
6. Nektar Therapeutics (Nasdaq: NKTR)          short ratio: 12.3
7. Exelixis (Nasdaq: EXEL)                     short ratio: 11.8
8. Mylan (Nasdaq: MYL)                         short ratio: 11.7
9. Salix Pharmaceuticals (Nasdaq: SLXP)        short ratio: 11.6
10. Vertex Pharmaceuticals (Nasdaq: VRTX)      short ratio: 10.8

11. BioMarin (Nasdaq: BMRN)                    short ratio: 10.8
12. Protalix BioTherapeutics (AMEX: PLX)       short ratio: 9.3
13. Xenoport (Nasdaq: XNPT)                    short ratio: 8.9
14. Regeneron Pharmaceuticals (Nasdaq: REGN)   short ratio: 8.0
15. Cephalon (Nasdaq: CEPH)                    short ratio: 7.4
16. Hi-Tech Pharmacal (Nasdaq: HITK)           short ratio: 7.4
17. Anika Therapeutics (Nasdaq: ANIK)          short ratio: 7.4
18. Abraxis Bioscience (Nasdaq: ABII)          short ratio: 7.1
19. Warner Chilcott (Nasdaq: WCRX)             short ratio: 6.9
20. United Therapeutics (Nasdaq: UTHR)         short ratio: 6.7

The short ratio is simply: Short Interest /Average Daily Trading Volume and it tells us how long, in terms of a stock’s daily trading volume, it would take to unwind all the shares of a stock that are sold short.