(DURHAM, N.C.) -- Despite promising results in clinical trials, the Food and Drug Administration has denied to approve several weight loss drugs over the years, further limiting people's resources in fighting obesity and weight gain.
One such disapproved drug is Qnexa -- an experimental weight loss drug that combines phentermine with topiramate, a drug approved for epilepsy and migraine prevention.
In a clinical trial at North Carolina's Duke University, 995 patients who received Qnexa in the phase three trial averaged a weight loss of 9.8 percent, compared to 1.2 percent among 994 patients who received a placebo. The trial findings were published April 9 in The Lancet.
But despite the noted effectiveness, the FDA rejected an application from drug maker Vivus to have Qnexa approved for the treatment of obesity, citing safety concerns. Qnexa was associated with a low but increased risk of psychiatric and cardiovascular adverse events.
"As clinicians and clinical researchers, we'd all consent that the FDA seem to have set a very different safety bar for drugs that treat weight loss compared to drugs that treat other conditions," said Dr. Kishore Gadde, director of Duke's obesity clinical trials program and lead author of the study.
Qnexa was one of three weight loss drugs nixed by the FDA in 2010.
"We need more options to treat obesity," Gadde said. "In hypertension, you have about 40 to 50 drugs with different mechanisms. In obesity, when you try diet and exercise and it doesn't work, you only have one drug before you jump to last resort, which is surgery."
The single drug approved for the treatment of obesity -- orlistat (Xenical or Alli) -- acts by preventing the absorption of dietary fat. But it doesn't quash hunger.
"People know they should cut down on calories. But if you only have orlistat, how do you deal with a patient who comes to you and says, 'I know all this stuff but I cannot control my hunger?' For that patient orlistat won't work," Gadde said.
Vivus is in talks with the FDA to address any outstanding safety concerns, according to company president Peter Tam.
Gadde and Tam said they think the FDA is being hard on weight loss drugs because of the number of Americans who would use them.
Copyright 2011 ABC News Radio