Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of VIVUS (NASDAQ:VVUS), manufacturer of the FDA-approved chronic weight management pill Qsymia, slumped as much as 12% after reporting its fourth-quarter earnings results.

So what: For the quarter, VIVUS reported product revenue of $2 million and a loss of $0.56 per share compared to just $0.13 last year as marketing expenses have risen dramatically. Wall Street had been looking for VIVUS to report sales of $3 million and a much smaller loss of just $0.25 per share. All told, VIVUS has now filled approximately 57,000 prescriptions of Qsymia, with 17,400 of those coming in the latest rolling month ended Feb. 15.

Now what: We sort of knew to expect that Qsymia's sales figures weren't going to be great, but even I was sort of surprised at how rapidly costs rose and sales slumped. With Aetna on board and covering Qsymia, it seems to me only a matter of time until other insurers join the fray. What will really differentiate whether VIVUS is successful will be its ability to sell Qsymia once Arena Pharmaceuticals' (NASDAQ:ARNA) Belviq makes it to market in the U.S., and, how long, if ever, it'll take Qsymia to get approved in Europe. The Committee for Medicinal Products for Human Use recommended further safety testing be done on Qsymia by rejecting VIVUS' appeal last week, so it looks like a long road from that respect. Luckily for VIVUS shareholders, things aren't looking like smooth sailing for Arena's Belviq, either, with the EU panel requesting additional information regarding the risks and benefits associated with the drug in January. For the time being it looks like VIVUS shareholders are going to be stuck in limbo.

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