July 15, 2010
Weight Loss Drug Too Dangerous to Be Allowed On Market
Public Citizen’s Dr. Sidney Wolfe Testifies Before FDA Advisory Committee
Dr. Sidney Wolfe, director of Public Citizen’s Health Research Group, testified today before an FDA advisory committee about a proposed new weight-loss drug, Qnexa. In his testimony, prepared by himself and Dr. Charles Preston of the Johns Hopkins Bloomberg School of Public Health, he said the drug is too dangerous too approve. Qnexa is a combination of two old drugs, phentermine and topiramate, each of which has significant risks. One is an amphetamine; the other, an anti-seizure medication.
Phentermine affects many different organ systems, including the neurologic, cardiovascular, and gastrointestinal. It increases heart rate and blood pressure, heightens wakefulness, and decreases appetite.
Studies of topiramate show that cognition is impaired in people who take the drug, particularly regarding attention, memory, and language. The same is seen with Qnexa. It was hypothesized that by adding an amphetamine, the negative cognitive effects of topiramate might be mitigated. But we see just the opposite-that the combination is worse than the topiramate alone. Further, anti-epileptic drugs – especially topiramate – have long been known to increase the risk of suicidal ideation relative to placebo.
Qnexa carries a long list of serious side effects. In fact, adverse events were the major reason patients failed to complete the trials of the drug; 18% of high-dose subjects withdrew due to an adverse event, compared to 9% for a placebo.
Perhaps one of the most important prior studies relevant to today’s decision was a randomized, placebo controlled trial of topiramate controlled release (CR) for overweight and obese patients with type 2 diabetes. The treatment group underwent 16 weeks of therapy, up to a dose of 175 mg/day. The investigators found that the cognitive and psychiatric effects were similar to those seen with Qnexa– namely higher rates of anxiety, memory difficulties, and insomnia compared to placebo– and they concluded that the “CNS and psychiatric adverse event profile of topiramate CR makes it unsuitable for the treatment of obesity and diabetes.” “We couldn’t agree more strongly,” Dr. Wolfe said.
To read the testimony, visit https://www.citizen.org/our-work/health-and-safety/articles/testimony-phentermine-and-topiramate-qnexa.