Qsymia, the combination diet drug composed of phentermine and topiramate, was approved by the FDA in July of 2012. Now, the results of a study conducted between December 2007 and September 2008 and originally submitted to the FDA to support approval for this drug show that it is even more effective than originally thought. The study was recently published in the journal Obesity.
Researchers from Weill Cornell Medical College in New York City and colleagues divided about 750 obese adults with BMIs between 30 and 45 kg/m2 into eight groups seven treatment arms and one placebo group. The treatment arms included two doses of phentermine, two doses of topiramate ER and two doses of Qsymia. A lifestyle intervention was also included in the intervention which consisted of counseling on reducing energy intake by 500kcal/day, keeping a food diary and increasing physical activity. The main outcomes measured were percentage of initial weight lost and participants achieving at least five percent weight loss by the end of the 28-week study. Researchers found that the percentage of subjects who lost 10 percent or more of their body weight was highest among those taking Qsymia in either dose compared to those taking the individual drugs or a placebo. Adverse events were monitored but were mild to moderate and included paresthesia (tingling of the skin), headache, dry mouth and constipation.
The drug, only on the market for 13 months, is not selling as expected but Barbara Troupin, vice president for scientific communications and risk management at VIVUS, thinks things will change soon. She says, It has been 13 years since a new obesity drug has come on the market. Clinicians are not in the habit of prescribing medications for obesity, but the AMA has declared obesity a disease and more attention is being paid to this issue.
ACSH s Dr. Josh Bloom says, Since the 1997 fen-phen debacle, when Wyeth withdrew the popular (and highly effective) diet drug Redux (aka fen-phen) after reports of damage to heart valves and a life-threatening condition called primary pulmonary hypertension, drug companies and regulators have been treating diet drugs like poisonous snakes. But this was an overreaction. The heart and lung toxicity of fen-phen was definitively traced back to a specific metabolite of fenfluramine (the fen component). It is physically impossible for this metabolite to be formed from either component of Qsymia. Eventually doctors and patients will realize this and I expect a much wider use of this implorant drug.
Dr. Bloom has written an op-ed that explains this in more detail. It is entitled Qsymia is not Fen-Phen.