5 Experts Answer: Could Qnexa Help You Lose Weight?

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The weight loss drug Qnexa is likely to be approved by the Food and Drug Administration in the next month, experts say.

Last week, an FDA panel voted in favor of the drug's approval, and the agency usually follows the advice of its panels. The decision is a turn-around from a string of recent disapprovals for similar drugs, including the weight-loss drug Contrave, which was rejected by the FDA last year.

But is Qnexa a practical way to lose weight? Here's what five weight-loss experts had to say.

Dr. Pieter Cohen, assistant professor of medicine at Harvard Medical School and a general internist at Cambridge Health Alliance:

"It's likely that the FDA will soon approve Qnexa for weight loss. This is unfortunate. Qnexa does help some people lose a modest amount of weight, but to keep the weight off, one has to take Qnexa for a lifetime. But we have no idea if Qnexa is safe to use for a lifetime. In fact, there are many early findings that suggest it might lead to serious health problems such as seizures, birth defects, kidney stones, confusion and heart disease.

"In my opinion, it is likely that Qnexa will follow in the footsteps of Meridia. Meridia was touted as a magic bullet for safe weight loss only to be withdrawn from the U.S. after careful studies revealed that it actually increased the risk of heart attacks and strokes.

"Assuming Qnexa is approved, what do I recommend? It will be very tempting to try a new diet pill once the FDA gives it their blessing, but in the case of Qnexa: just say no. Stick with the hard work of increasing exercise, modestly decreasing calories and selecting healthy foods.

"For certain people, gastric bypass might be the right answer, but there's not a pill around that's worth its weight."

Dr. Olveen Carrasquillo, chief of general medicine at the University of Miami Miller School of Medicine:

"Qnexa, like other such agents, can definitely achieve short-term weight loss. The big question is whether that short-term weight loss is permanent… over several years. In fact, periodically going up and down in weight is probably more dangerous than maintaining a stable weight.

Further, what I would need to know is if the weight [stays] off over several years. Then, does it also result in improved health outcomes over the long term — less diabetes, less hypertension, improved health and functional status and lower mortality rates over several years.

"If the drug does not lead to long-term lifestyle changes, I am doubtful of any such long-term benefits.

"Like many other doctors, I do my best to avoid prescribing any new mediations for the first few years after approval, unless they are critical. This allows time to have better post marketing data on long-term side effects.

"Also, I would be extremely leery of using this drug in any woman of child-bearing age."

Dr. David Katz, director of the Prevention Research Center at Yale University School of Medicine:

Yes, [Quenexa] can help you lose weight. But that doesn't mean it will, or even that it should.

Qnexa combines a stimulant drug with an anti-epilepsy drug. The first can drive up blood pressure, and can [cause] jitteriness. The second can cause fatigue, nausea and brain fog. It's not a great drug by any means, and likely only works as long as people keep taking it.

For those facing bariatric surgery, it is an option worth considering, although not as effective. For most others, better use of feet and forks is the far better option.

Dr. Michael Aziz, internist at Lenox Hill Hospital in New York City:

"Qnexa combines phentermine (the other half of fen-phen) and topiramate (sold as Topamax). When Qnexa was compared with a placebo pill, weight loss patients that were treated with Qnexa for two years showed reductions in blood pressure, in addition to positive improvement in lipid levels following reductions in weight loss. However, there are other concerns, such as psychiatric problems, as well as issues with birth defects.

"Phentermine is known to cause elevation in blood pressure. Topamax has [more] serious side effects which are described in drug safety inserts and they include: paresthesia or "pins and needles," most often in the arms or legs, fatigue, taste change, difficulty with concentration and weight loss. Now we can understand how weight loss became a desirable side effect to combine this Topamax with phentermine.

"Yes, Qnexa may help many, but lifestyle and the right diet should be the first focus and primary targets to address for those who are struggling with weight and need a real, and a permanent solution."

Dr. Sunil Bhoyrul, bariatric surgeon at Scripps Memorial Hospital in La Jolla, Calif.

"Any strategies to help people lose weight should be seriously considered. [But] it's oversimplifying to say give everyone Qnexa.

"For the day to day reality of taking care of patients, we know that you need a whole array of treatment options."

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Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.