Drug companies are once again trying to get weight-loss drugs back on the market after a series of high-profile recalls.
On Thursday, the U.S. Food and Drug Administration will review the efficacy and safety of Qnexa, one of three new weight-loss drugs.
Experts hope Qnexa, and the other drugs, Lorcaserin and Contrave, will provide effective weight-loss without the dangerous side effects that doomed other drugs, such as Fen-phen, Meridia and Alli. Fen-phen was pulled from the market in 1997 after it was linked to a thickening of the heart valve. Meridia was pulled from the European drug market in 2009, and the FDA recently warned consumers about Alli's link to severe liver damage.
So far Qnexa has reported positive results.
"It's shown a 10 to 15 percent weight-loss in patients, which is very impressive," said Dr. Ken Fujioka, director of the Scripps Clinic Center for Weight Management in San Diego. He is also on the advisory committee for Vivus, the company that makes Qnexa, as well as on the advisory committees for the companies that make Lorcascerin and Contrave.
Qnexa contains the amphetamine phentermine -- one half the ingredients of the popular combination diet pill Fen-phen, ultimately pulled by Wyeth, its manufacturer in 1997 because of its link to heart damage.
Fujioka said although it proved dangerous in the combination, there were no safety issues with phentermine by itself.
According to Vivus, Inc., the company that makes Qnexa, phentermine helps suppress a person's appetite, while the other ingredient, the anti-convulsant topiramate, makes a person feel more satiated.
Some experts though, questioned the safety of a combination pill that appears to show striking similarities to previously recalled drugs.
"Whether any drug will become another Fen-phen is hard to predict," said Dr. Gerard Mullin, associate professor of medicine at the Johns Hopkins School of Medicine. "Every time we see a drug recalled, none were predictable, but it seems that similar classes of drugs can have inherent problems."
It's also unclear to some experts on whether topiramate actually works.
"The anticonvulsant in both Contrave and Qnexa is a new variation on the theme of tweaking brain pathways to adjust appetite but does not appear to be more than a minor innovation to me, and one of questionable utility," said Dr. David L. Katz, associate professor adjunct in public health practice at the Yale School of Public Health.
"We did very detailed studies and found it wasn't the phentermine. It was phenfluramine that was linked to the heart issues," Katz said.
Fujioka said the trials for Qnexa, Lorcaserin and Contrave lasted about a year. The drugs were tested on about 4,500 patients each.
However, others believe there have not been enough studies done to show that these drugs are safe for most patients.
"Just because these compounds don't have the same chemical mix as Fen-phen doesn't mean they don't have a chemical mix that can cause long-term harm," said Joanne P. Ikeda, nutritionist emeritus and former co-director of the Center on Weight and Health, University of California, Berkeley. "I think we should demand long-term (three- to five-year) safety studies for these drugs."