Why Have Diet Pills Containing Sibutramine Been Banned?

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Diet pills often promise a miracle in a bottle, but what they sometimes deliver isn't worth the magic. In October, the Food and Drug Administration (FDA) announced that Meridia, which contains the compound sibutramine, has been withdrawn from the U.S. market after a clinical trial revealed an increased risk of heart attack and stroke among those taking the obesity drug.

"Sibutramine was prescribed to patients because it was shown to cause a modest amount of weight loss in the early trials," said Dr. Pieter Cohen, an assistant professor of medicine at Harvard Medical School and a general internist who researches adverse effects of dietary supplements at the Cambridge Health Alliance.

This, however, reveals a potential flaw in the approval process. "The FDA approves medication based on the short-term changes they produce, not the long-term changes," Cohen told Life's Little Mysteries. "The patients taking these drugs can come across problems down the road meanwhile, the drug has already been approved."

Meridia, which the FDA approved in 1997, was banned in Europe after a 2009 study called Sibutramine Cardiovascular Outcomes Trial (SCOUT), part of a post-market requirement to examine the cardiovascular safety of sibutramine after the European approval of the drug, showed a 16 percent increase in the risk of serious cardiovascular events compared with those taking a placebo. It continued to be sold in the U.S., however, until the FDA requested that its manufacturer, Abbott Laboratories, voluntary withdraw Meridia.

The study, which was conducted in Europe, Latin America and Australia, monitored about 10,000 obese and overweight men and women between January 2003 and March 2009, also showed that Meridia increased the risk of non-fatal heart attack, non-fatal stroke, the need to be resuscitated once the heart stopped and death. The drug, which was intended to decrease the risk of heart disease in obese people by helping them lose weight, was actually doing the opposite, Cohen said. The study showed that people on the drug actually had their risk of heart attack and stroke spike by 16 percent. Making matters worse, they lost only a minor amount of weight, just 2.5 percent more, on average, than those who took the placebo.

"With obesity medication, there needs to be more serious testing before they're allowed to be distributed to the public," Cohen said. "The FDA needs to consider a drug's long-term changes."

Despite the U.S. ban of sibutramine, weight-loss drugs containing the ingredient can still be easily bought online. The FDA has issued warnings that several diet pills that don't list sibutramine as an ingredient on their labels have tested positive for it. Consumers looking to drop a few pounds buy pills falsely marketed as "herbal" and "all-natural," and unknowingly ingest sibutramine.

Last March, the FDA arrested traffickers of tainted weight-loss pills and counterfeit drugs who had sold counterfeit versions of the drug "Alli" and sibutramine-laced pills under the names of Superslim 2 Day Diet and other weight loss products believed to have been imported from China and subsequently marketed as dietary supplements or nutritional products, according to the FDA.

"The people selling these weight-loss drugs are criminals, they're not going to be honest about what they're putting in them," Cohen said. "There is no strong data supporting that any herbal ingredients are effective in weight loss. Anyone taking them and losing weight should be extremely concerned, as they might actually be ingesting an illegal, dangerous product."

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Remy Melina was a staff writer for Live Science from 2010 to 2012. She holds a bachelor’s degree in Communication from Hofstra University where she graduated with honors.