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FDA Reconsiders Weight Loss Drug Qnexa

Weight Loss Impressive, but Safety Questions Remain
WebMD Health News
Reviewed by Laura J. Martin, MD

Nov. 9, 2011 -- The FDA is again considering approval of an experimental weight loss drug it rejected a year ago over concerns about potential heart problems and birth defects in babies born to women who take the drug.

California-based pharmaceutical company Vivus Inc, is now asking for limited approval for its oral combination drug Qnexa, which would exclude women in their childbearing years.

According to the company, the FDA is scheduled to make an approval decision next April. If approved, the drug could be commercially available soon after that.

That would make Qnexa the only prescription appetite suppressant approved for long-term use available in the U.S. The only other widely marketed prescription weight loss drug, orlistat -- sold by prescription as Xenical and over-the-counter as Alli -- works by blocking dietary fat absorption.

In a study submitted to the FDA last year in Vivus’ original filing, and published in the journal Obesity late last week, people who took the highest dosage of Qnexa for a year lost, on average, about 14% of their body weight. They showed improvements in blood pressure, cholesterol, triglycerides, and blood sugar.

Qnexa Combines Two Drugs

Qnexa combines low doses of the stimulant phentermine -- long used for short-term weight loss -- and the anti-seizure and migraine drug topiramate, which has also been used "off label" to treat binge eating. "Off label" refers to drugs that are prescribed by doctors as treatments for conditions that are not specifically approved by the FDA.

Last fall, an FDA panel voted against the drug’s approval, citing North American drug registry data showing that babies born to women who took topiramate had up to a 20-fold increase in cleft palates.

Vivus Inc. president Peter Tam tells WebMD that subsequent investigations involving other databases suggest that the risk for the oral birth defect is actually much lower.

Based on the new information, the FDA agreed to let the company resubmit its application for limited approval for use in adults who are not likely to become pregnant.

At the request of the FDA, the company is also examining more than a decade of medical claims records involving women who took topiramate during pregnancy to treat seizures, migraines, and other conditions, Tam says.

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