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Diet Drug Lorcaserin Safe, Effective, Study Finds

Half of Dieters Lost 5% of Their Body Weight in a Year
WebMD Health News
Reviewed by Laura J. Martin, MD

July 14, 2010 -- An experimental weight loss drug that targets the brain’s hunger center was shown to be safe and effective for helping dieters shed pounds in a two-year study, researchers say.

The drug lorcaserin works on the serotonin receptor -- the same appetite-controlling hormone targeted by the notorious drug fenfluramine, the "fen" component of combination medication fen-phen. Fenfluramine was taken off the market in 1997 after being linked to potentially life-threatening heart valve problems.

But lorcaserin is far more selective than the drug fenfluramine and much safer, its manufacturer says, because it specifically targets the serotonin receptor associated with hunger while having no impact on the heart.

Half Lost 5% of Body Weight

About half the dieters who took lorcaserin for a year in the study lost at least 5% of their body weight, compared to 20% of dieters who took a placebo pill. About one in five lorcaserin users lost 10% or more of their body weight, compared to one out of 14 placebo users.

People who continued on the drug for two years were able to maintain their weight loss better than those switched to placebo after one year, researcher Steven R. Smith, MD, of the Florida Hospital and the Sanford-Burnham Institute tells WebMD.

He says that all the patients in the study were monitored closely for heart valve irregularities, and no difference was seen in the two treatment groups.

The study appears in the July 15 issue of the New England Journal of Medicine.

It was funded by Arena Pharmaceuticals, Inc., which developed lorcaserin. The company hopes to win FDA approval to market the new drug later this year.

Diet Drug Users Lost Twice as Much Weight

The study included about 3,200 obese or overweight adults who were randomly assigned to take 10 milligrams of the diet drug or placebo, twice a day for a year. All the participants were counseled about diet and exercise.

By the end of year one, 55% of the patients in the placebo group and 45% of those taking the diet drug had dropped out of the study.

During the second year, half of the remaining participants who had been taking lorcaserin were switched to placebo.

The average weight loss during the first year was about 12 pounds in the lorcaserin group and 5 pounds in the placebo group. During the second year of the study, 68% of people who continued to take the weight loss drug maintained the loss vs. 50% of people switched to placebo.

The most frequently reported adverse events were headache, dizziness, and nausea, but Smith says these symptoms tended to resolve after a few weeks.

Expert: ‘Modest Weight Loss, Good Safety Profile’

In an editorial accompanying the study, obesity researcher Arne Astrup, MD, who heads the department of nutrition at the University of Copenhagen, writes that the weight loss achieved with the drug was slightly less than has been typically reported for the two available prescription weight loss drugs in the United States, Meridia and Xenical.

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