The FDA has approved the first drug to treat one form of irritable bowel syndrome (IBS) in women. Novartis Pharmaceuticals ' Zelnorm (tegaserod maleate), primarily for women whose main IBS symptom is constipation, will be released early this fall.

The FDA pointed out that Zelnorm doesn't cure IBS and is not for treating IBS whose main symptom is diarrhea. The FDA's approval decision was based on three studies during which, in a three-month period, the drug was shown to reduce constipation, bloating and abdominal discomfort. The FDA noted that effects were greatest after one month, reducing each month thereafter. Effects after three months were not studied.

Novartis said Zelnorm is the first in a new class of drugs called serotonin-4 receptor agonists, activating these receptors to stimulate the peristaltic reflex to normalize the gastrointestinal tract's motility. Side effects include headaches and diarrhea. Novartis also noted there are no marketing restrictions in place for Zelnorm, unlike the earlier drug for IBS from GlaxoSmithKline, Lotronex, that was removed from the market in 2000 for safety concerns. Novartis estimates the potential market for its new drug is 10 million women in the U.S. The drug is already approved in 30 other countries. Finally, Novartis is investigating the use of Zelnorm for other disorders, including chronic constipation and indigestion.