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), a biopharmaceutical company focused on developing drugs to treat obesity, diabetes, and sexual health, rocketed higher by as much as 18% after the company announced the supplemental new drug approval by the Food and Drug Administration for erectile dysfunction drug Stendra.

So what: Developed by Auxilium Pharmaceuticals (NASDAQ: AUXL) and VIVUS, Stendra was originally approved in 2012. Today's sNDA allows Stendra to be taken as early as 15 minutes prior to sexual activity with or without food, and with moderate alcohol consumption. Relative to the placebo in studies, Stendra helped men achieve an erection in as quickly as 15 minutes, making it a fast-acting erectile dysfunction option. Prior ED medications required patients to take a drug at a minimum of 30 minutes prior to sexual activity, which implies that the improved reaction time of the drug could make it a popular choice by physicians and patients.

Auxilium has exclusive marketing rights to Stendra within the U.S. and Canada, while VIVUS owns the worldwide development and commercial rights for Stendra, with the exception of select Asian countries.

Now what: Obviously, seeing the FDA expand Stendra's label is good news for VIVUS, as it could help expand the company's revenue potential. On the other hand, it's also worth keeping in mind that the ED market is highly competitive (a number of other ED drugs are in clinical development), so it's not as if Stendra/Spedra (as it's known overseas) is going to have the market all to itself.

We also can't have a discussion of VIVUS without discussing the massive disappointment that weight control management drug Qsymia has been. Though Qsymia offered intriguing weight-loss percentages in clinical trials relative to Arena Pharmaceuticals' (NASDAQ:ARNA) Belviq and Orexigen Therapeutics' (NASDAQ: OREX) Contrave, both Belviq and Contrave arguably have a more favorable safety profile relative to Qsymia -- and both physicians and patients appear to be shying away from Qsymia; there were just $11 million in Qsymia product sales last quarter. Having been on pharmacy shelves for two years and originally boasting a peak sales potential north of $1 billion, Qsymia has largely been a disappointment.

As of now, VIVUS appears to be nothing more than a highly speculative investment. Though it has $104 million in net cash, VIVUS' clinical studies and marketing costs for Qsymia are expected to cause it to burn around $100 million annually through 2015. That is enough reason for me to stay far away from this stock for the time being.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.