Qnexa Diet drug rejected by FDA to be reviewed again

The F.D.A. rejected Qnexa in 2010, amid safety concerns, and the drug’s manufacturer is now presenting additional data to argue its case.

But thousands of people in central California, where Qnexa’s inventor ran a weight-loss clinic, and others across the country have not had to wait for the drug’s approval. Through a regulatory loophole of sorts, many obesity doctors prescribe two separate drugs that, when taken together, are essentially the same medicine.

“I can’t tell you how many people I sent to him because they saw the success I had,” said Lynn Adams, a retired teacher, referring to Dr. Thomas Najarian, the inventor of Qnexa who opened a weight-loss clinic here in 2001.

Ms. Adams said she took the two drugs for a year and lost about 80 pounds. She has taken the drugs from time to time since then but is off them now and has gained about half the weight back.

Qnexa, developed by the company Vivus, is a combination of two already approved drugs — a stimulant called phentermine and an anticonvulsant called topiramate — that seem to work together to quell appetite. Even though the F.D.A. declined to approve Qnexa two years ago, citing the risks of birth defects and cardiovascular problems, doctors are allowed to prescribe the components off-label as they see fit.

Many do. Dr. Christopher D. Still, director of the obesity institute at Geisinger Health System in Danville, Pa., estimated that 70 percent of obesity specialists prescribed the combination. “There is a subgroup of individuals that really feel satiated” when treated with the two drugs, said Dr. Still.

Only one drug, Roche’s Xenical, is currently approved for long-term use in treating obesity, and it is unpopular because of embarrassing digestive side effects. The F.D.A. rejected three obesity drugs, including Qnexa, in 2010 and 2011, citing different safety concerns for each.

On Friday, the F.D.A.’s staff released its analysis of the new Qnexa data and said it was still concerned about potential heart problems and birth defects in women who become pregnant while taking the drug. On Wednesday, an advisory panel will review the drug and make its recommendation. The staff will ask the committee to consider whether Vivus should do a large clinical trial to judge cardiovascular risks before the drug can be approved.

The F.D.A. will have until April 17 to make a decision about it.