In late February an F.D.A. Advisory Panel overwhelmingly recommended approval of Qnexa for the treatment of obesity. Studies showed that participants lost about ten percent of their body weight after a year on the drug although some weight was regained during the second year.
Qnexa is a combination of two medications that are currently available by prescription: phentermine, a stimulant approved for short-term (12 weeks) appetite suppression, and topiramate, an anticonvulsant used to treat epilepsy and migrane headaches.
Currently phentermine is widely used in weight loss clinics. It was the benign part of the phen-fen combination drug which was withdrawn in 1997 because of heart valve problems that resulted from the combined medication.
The positive Advisory Panel recommendation was surprising because a previous Advisory Panel had reviewed Qnexa in 2010 and voted 10 - 6 against approval. The previous panel rejected it because of increased risks of birth defects and cardiovascular problems associated with the drug. The F.D.A. followed the panel's advice and rejected the drug but will revisit Qnexa and make it's decision by April 17th. This time it's likely that Qnexa will be approved since the F.D.A. usually, but not always, follows the Panel's recommendation. To minimize health risks it's likely that there will be restrictions intended to prevent pregnant women from taking the drug.
It won't be an easy decision for the F.D.A.. Since Meridia was withdrawn from the market in October 2010 the only drug currently approved for long-term treatment of obesity is Xenical. It isn't widely used because of minimal weight loss and very unpleasant digestive problems. With two thirds of the population obese or overweight, and the only other alternative to a diet and exercise regimen is bariatric surgery, an effective weight loss medication would be widely prescribed.
What should the F.D.A. do? While lifestyle changes can produce weight loss the unfortunate reality is that we live in an obesigenic environment. With all the food cues, the prevalence of calorically dense foods, and the ever increasing portion sizes (at home too - not just at McDonald's) it's difficult for most people to lose weight. Any medication that produces significant weight loss would be welcomed. Also, since phentermine and topiramate are currently available there's nothing to prevent physicians from prescribing them even if Qnexa isn't approved.
In addition to the concerns about possible side effects, especially for pregnant women, the evidence so far suggests that the weight lost with Qnexa is regained after going off the drug. Rather than regaining the weight it's likely that people will continue using the drug indefinitely. However there are many drugs that are prescribed for indefinite use. For example, blood pressure meds are widely prescribed even though blood pressure usually could be reduced by lifestyle changes (lose weight, reduce sodium intake, etc.) instead of taking a pill.
Unfortunately there's no data on the effects of long-term use of Qnexa but it could be argued that the effects of long-term obesity are well established: increased risk of diabetes, cardiovascular disease, and some types of cancer. Whether it is approved or rejected, the F.D.A. decision will be controversial. Unfortunately, there's no easy answer to the nation's obesity problem.