WASHINGTON - Novartis AG’s  irritable bowel drug Zelnorm will come with a new warning that patients could experience severe diarrhea that requires hospital treatment, U.S. regulators said Wednesday.

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The drug’s new label also will caution about cases of reduced blood flow to the intestines, or ischemia, in patients who took Zelnorm, the Food and Drug Administration said.

It is not clear if Zelnorm played any role in the approximately 23 ischemia cases reported to regulators, said Dr. Robert Justice, director of the FDA’s gastrointestinal drugs division. Three of the patients needed surgery and four died, he said.

Sixteen Zelnorm patients were hospitalized for dehydration from severe diarrhea, Justice said.

Patients treated with Zelnorm should stop taking the drug immediately and contact their doctors should they develop new or more severe stomach pain or blood in the stools, Justice said.

“At the present time, we believe the benefits (of Zelnorm) outweigh the risks. We will continue to monitor” possible side effects, Justice said in an interview.

Swiss pharmaceutical company Novartis and some industry analysts had predicted peak annual sales of prescription Zelnorm would hit $1 billion worldwide.

The company is sending letters with the updated information to more than 450,000 doctors and pharmacists, spokeswoman Carrie Callahan said.

Severe side effects rare
Severe diarrhea is rare, Callahan said. In clinical trials, it occurred in only 0.04 percent of patients.

She also said the rate of bowel ischemia cases reported after the drug’s approval in July 2002 was small and similar to what is expected in the general population.

But consumer watchdog Sidney Wolfe said Zelnorm is too dangerous to stay on the market and only slightly more effective than a placebo. He had urged the FDA not to approve the drug in the first place.

“If a drug is actually more dangerous than a placebo and not much more effective, it is a very bad trade-off,” Wolfe, head of Public Citizen’s Health Research Group, said in an interview.

Irritable bowel syndrome, or IBS, causes alternating bouts of diarrhea and constipation as well as abdominal pain. Zelnorm is approved for short-term treatment of women with IBS whose main symptom is constipation.

Another irritable bowel drug, GlaxoSmithKline Plc’s Lotronex, was pulled from the U.S. market after reports of fatal cases of bowel ischemia. The FDA later allowed limited sales to resume.

Lotronex is approved for treating women who suffer mostly from diarrhea.

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