2. Risky side effects It is true that in clinical trials VIVUS' Qsymia pill appeared more effective in treating obesity than Arena's Belviq. However, that advantage comes at a potentially dangerous price. Patients prescribed Qsymia risk serious heart conditions, and pregnant women can't use the drug given possible birth defects. Comparably, cardiovascular issues have held back Orexigen Therapeutics ' ( NAS: OREX ) anti-obesity drug, Contrave. Orexigen will have to wait until next year before it can resubmit new clinical data to the FDA, with hopes of proving that its medical weight-loss treatments are safer than previously demonstrated. Meanwhile, VIVUS must still jump through some safety hoops of its own. In fact, the FDA is requiring that the drugmaker carry out 10 additional safety studies once Qsymia is available to patients. Of course, there's always a chance that VIVUS' drug gets pulled late in the game over such safety concerns.