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Zelnorm Deemed Safe for IBS Constipation

Watchdog Group Still Worried, but GI Docs Happy
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WebMD Health News

Editor's Note: In March 2007 the FDA asked Novartis -- the maker of Zelnorm -- to pull the drug from the market because of evidence that it raises the risk of heart attacks and stroke. But in July 2007 the FDA ruled that Zelnorm may be used by some patients in critical need of the drug who do not have heart problems.

Oct. 29, 2002 -- Zelnorm is safe for at least 12 months of use, say doctors who tested the newly approved drug for the constipating form of irritable bowel syndrome (IBS). But not everyone agrees.

Zelnorm -- known as Zelmac in Europe -- traveled a rocky road on its way to U.S. approval. Concerns that the drug might cause gallbladder problems held up approval for a year. Those fears proved groundless, experts tell WebMD.

However, the consumer watchdog group Public Citizen unsuccessfully petitioned the FDA to deny approval. It says the drug's small benefit in clinical trials doesn't justify the risk of possible side effects. And the group points to evidence that ovarian cysts -- sometimes requiring surgery -- could be a rare but serious Zelnorm side effect.

One reason for concern is recent history. Zelnorm affects the serotonin system, a complex series of chemical signals that keep the body in synch. Two other digestive system drugs that affect this same pathway system recently ran into problems. Propulsid was taken off the market when it turned out to harm the heart. And Lotronex, a drug for IBS diarrhea, can cause life-threatening constipation.

So there's lots of interest in a new study that followed 579 patients who were supposed to take Zelnorm for one year. About half of them stopped taking it, but only a few stopped because of side effects. Those who kept taking the drug had very few problems. One patient did develop an ovarian cyst, but lead researcher Gervais Tougas, MD, says it appeared unrelated to the medication. Tougas is director of the gastrointestinal motility laboratory and chief of gastrointestinal Services at St. Joseph's Hospital in Hamilton, Ontario. His study appears in the current issue of Alimentary Pharmacology and Therapeutics.

"There is nothing in these data to support the idea that this [ovarian cyst] is a signal that such problems happen with increased frequency in [people who take] Zelnorm," Tougas tells WebMD.

The data show nothing because the study was poorly designed, counters pharmacologist Elizabeth Barbehenn, PhD. Barbehenn is a former FDA scientist who now serves as a research analyst for Public Citizen.

"It's a big joke," Barbehenn tells WebMD. "There was no control group, so you could say anything you want. Half the people dropped out before the study ended. And there was no protocol for whether the drug caused problems. They let the investigators just decide whether they thought adverse events were related to the drug."

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