You can't trust the daily short volume figures. ARNA traded 21.3 million shares on Friday. But the short volume numbers are based on a volume of only 13 million. Also, the daily short volume is not a daily net. It does not indicate how much of that short volume was covered intra-day.
As best I can tell, there were 40+ million shorts going into June 27 when belviq was approved. Obviously, a heavy short interest does not always indicate that the shorts know something. Those shorts should have fried, but instead they shorted and bashed more trying to cap the usual post-approval spike. On Friday June 29th, the short interest was 46 million shares, more than it has been all year.
Right now I see a bunch of trapped shorts working very hard to hold the pps back and hoping and praying that a qnexa approval (of any kind) will give them an opportunity to unwind those positions in a less painful way.
I am braced for the storm of anti-belviq nonsense that is sure to come this week. Even if qnexa is rejected or delayed, the belviq bashers will be out in force trying to take the edge off the shorts' pain.