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Clinical trials for new diet pill show promise

The recent trial of an experimental diet pill shows promise for medicated weight loss.

The 56-week CONQUER study, which was published April 16 in The Lancet, showed that a treatment combining phentermine and topiramate resulted in weight loss of up to 10 percent of patients’ body weight in a year. The study involved 2,487 patients who were assigned either a placebo or one of two dosage levels of the drug combination. The combination, called Qnexa, was developed by pharmaceutical company Vivus Inc., which funded the study.

“Average weight loss was three pounds with placebo, 18 pounds with the lower-dose drug and 22 pounds with the higher-dose drug,” Kishore Gadde, director of Duke’s obesity clinical trials program and lead investigator of the study, wrote in an April 20 email.

Phentermine is currently used as a treatment for obesity and topiramate for epilepsy and migraines. Together, the drugs work to suppress appetite.

Gadde said combining drugs with different mechanisms at times leads to greater success.

“Phentermine... is believed to promote satiety (fullness) and suppress appetite. Topiramate is also believed to work by suppressing appetite via its effects on glutamate receptors in the brain,” Gadde said.

The Food and Drug Administration warned that topiramate may cause birth defects if taken while pregnant, but of the 34 women who became pregnant during the trial, no defects were reported, Gadde said in the news release.

Individually, phentermine and topiramate have FDA approval, but Qnexa was recently rejected by the FDA, which requested additional safety information, according to an April 10 Duke Medicine news release.

The government has historically been slow to approve obesity medications. The Obesity Society, a group that studies the causes and treatments of obesity, has closely followed the recent FDA trials of several anti-obesity medications, including Qnexa. In a Feb. 2 news release from the group, TOS President Jennifer Lovejoy criticized the FDA’s slow approval process.

“In the face of such a devastating, widespread and expensive public health crisis as obesity, it is baffling that the FDA has consistently denied approval for anti-obesity medications,” Lovejoy said.

Time magazine described the pill as a potential “silver bullet for weight loss,” but Gadde was reluctant to jump to conclusions.

“Over a year, this drug treatment achieved impressive weight loss. However, we do not know its long-term benefit,” Gadde said. “Since there are not head-to-head comparison trials or meta-analyses yet, we refrained from stating that the drug we tested was better than others.”

Dr. Peter English, professor of history and pediatrics, said people have been trying to find a magic pill for at least a century, but suggested that medicine is not the best answer for weight loss.

“I really don’t think that the issue here is medication,” English said. “There are no mysteries—we all have to eat less and exercise more and do it for the rest of our lives.”

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