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FDA Wants Irritable Bowel Drug Shelved

Public Citizen Has Warned of Zelnorm's Dangers for Years

By Mark Huffman
ConsumerAffairs.com

April 1, 2007

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The Food and Drug Administration has told Novartis Pharmaceuticals Corporation that it wants it to suspend marketing of Zelnorm, used to treat irritable bowel syndrome. The agency said it requested the voluntary action based on recent findings of an increased risk of serious heart problems associated with use of the drug.

But Public Citizen says there's nothing recent about and notes that in March 2001, it petitioned the agency not to approve Zelnorm because it was only marginally effective and posed serious safety concerns. Besides heart problems, risks included ovarian cysts and fainting spells.

"We noted in this petition that receptors with which this drug interacts exist not only in the intestinal tract ... but also in the heart," said Dr. Sidney Wolfe, M.D., director of Public Citizen's Health Research Group.

"We pointed out that cisapride, a gastrointestinal drug which also caused fainting and was taken off the market because of cardiac arrhythmias, also affected this same receptor in the heart," Wolfe said.

"Once again, the FDA has approved a drug with marginal effectiveness in the face of serious questions about its safety -- putting at risk the millions of people who have already used it," Wolfe said.

He noted that the FDA has only asked the company to withdraw the drug from the market despite "even clearer evidence of harm.

"This again raises questions about both the adequacy of the FDA's pre-approval review and post-marketing surveillance," Wolfe said..

Zelnorm was approved by the FDA in July 2002 for short-term treatment of women with irritable bowel syndrome whose primary symptom is constipation. It was subsequently approved in August 2004 for treatment of chronic constipation for men and women under age 65. Zelnorm is currently marketed in 55 countries.

There were 2.13 million prescriptions issued for Zelnorm in 2005 alone, making it one of the top 200 drugs in the U.S., according to Public Citizen.

FDA said it advises patients who are using Zelnorm to contact their health care providers to discuss treatment alternatives. Patients who are taking Zelnorm should seek emergency medical care if they experience severe chest pain, shortness of breath, dizziness, sudden onset of weakness or difficulty walking or talking, or other symptoms of a heart attack or stroke, the FDA said.

FDA said it had only recently become aware of the drug's hazards. Its statement did not make any mention of the agency's ignoring Public Citizen's petition six years ago.

"This decision reflects the FDA's commitment to continuously monitor approved drugs throughout their marketing life, and take action when we believe the risks exceed the benefits," said Dr. Douglas Throckmorton, Deputy Director for the Center for Drug Evaluation and Research. "Here, a potential risk of very serious harm to patients who have this non-life-threatening condition was recently identified, making this action necessary."

Throughout February and March 2007, Novartis reported to FDA the results of a new analysis of 29 short-term randomized, controlled clinical trials of Zelnorm. FDA has concluded, based on these data that for most patients the benefits of this drug no longer outweigh the risks, the agency said.

The analysis included more than 11,600 patients treated with Zelnorm and over 7000 patients treated with placebo. The data showed that the risk of serious cardiovascular adverse events (e.g., angina, heart attacks, and strokes) associated with use of Zelnorm is higher than with placebo treatment.

Thirteen Zelnorm-treated patients (or 0.1%) had confirmed cardiovascular ischemic events, and only 1 placebo-treated patient (or 0.01%) with an event.

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