Qsymia is a combination of two FDA-approved drugs: phentermine, a stimulant related to the amphetamines that suppresses the appetite, and topiramate, a drug used to treat migraines and epilepsy that has weight-loss side effects. Vivus emphasizes that the drug is intended to be used in combination with diet and exercise.
In June, the FDA approved another diet drug, lorcaserin or Belviq. The drug is also an appetite suppressant and intended for patients who are obese and have one additional weight-related health problem, such as high blood pressure, type 2 diabetes or high cholesterol. However, studies of Belviq found that patients lost about 4 percent of their body weight, compared with the 10 or 12 percent lost by Qsymia patients.
But Qsymia is not without drawbacks. When Qsymia's manufacturer, Vivus, initially submitted the drug for approval in 2010, the FDA voted it down, citing concerns over the potential for dangerous heart problems, birth defects and cognitive effects such as mental fogginess or lack of concentration in patients taking the drug.
The 2012 panel voted to approve the drug only with Vivus' assurances that the company would provide detailed information to physicians about the risks of the drug and how to manage them.
Still, doctors are mixed in their concern over the potential for side effects, particularly in light of the history of diet drugs, such as fen-phen, approved by the FDA, then withdrawn from the market over concerns about heart risks and other dangerous side effects.
"Honestly, I won't be surprised if adverse effects over time result in a reversal of the approval," said Dr. David Katz, director of the Yale Prevention Research Center. "But in the interim, it will help some people lose weight, and many others will try it, dislike it and stop, and gain the weight back."
Evans said she's gained about 20 pounds since she stopped taking Qsymia in 2009. She said the gain is due in part to an injury to her Achilles tendon that has kept her from being as active as she was. But she said she would definitely consider taking it again to help her bring her weight down.
"Just to know that it's available if I need it, that's a real nice little prize," she said.