Common symptoms of the intestinal disorder include cramps, gassiness, bloating, and changes in bowel habits. A frequent complaint is constipation.

The U.S. Food and Drug Administration has approved the Novartis Pharmaceuticals drug Zelnorm to treat women who suffer from frequent constipation attributed to IBS. The agency stresses that the drug doesn't cure the disease, nor has it been approved for use by men.

In a series of 12-week trials, Zelnorm's effectiveness in reducing constipation, abdominal pain and discomfort appeared to wane after one month. The drug's effectiveness beyond 12 weeks hasn't been studied, the FDA says.

Here is the FDA Talk Paper announcing the drug's approval. And here is a complete primer on Irritable Bowel Syndrome from the American Academy of Family Physicians.