Tegaserod (Zelnorm)...New Drug for IBS (cont.)

How does tegaserod work?

In animal studies, tegaserod has been found to bind to one subtype of serotonin receptor, the 5-HT4 receptor, and thereby stimulate contractions of the intestinal muscle. It also reduces the sensitivity of the intestinal pain-sensing nerves. Stimulating intestinal contractions speeds up transit of digesting food through the intestine thereby relieving constipation, while suppressing the pain-sensing nerves reduces abdominal pain.

How effective and safe is tegaserod?

A randomized, double blind, placebo-controlled, multi-center clinical trial evaluating the efficacy and safety of tegaserod has been published (Aliment Pharmocol Ther 200; 15: 1655-1666). More than 1000 patients (80% women) with constipation-predominant IBS were randomly assigned to receive either placebo or tegaserod for twelve weeks.

Tegaserod was found to be more effective than placebo in increasing the frequency of stools, relieving abdominal pain and discomfort, and decreasing the sensations of bloating among women subjects. There was an insufficient number of male participants to draw conclusions about the effectiveness of treatment in men. The beneficial effects of treatment started early (during the first week of treatment) and were sustained throughout the 12-week period of study.

Diarrhea was the only observed side effect. Diarrhea typically occurred early during treatment and quickly resolved even if treatment was continued.

There was no effect of tegaserod on blood counts, liver and kidney tests, EKG, blood pressure, pulse, and body weight. A medication similar to tegaserod, called cisapride (Propulsid), also stimulated intestinal muscle contractions, but cisapride was withdrawn from the market due to rare but potentially fatal effects on the electrical rhythm of the heart. So far, there have been no reports of rhythm disturbances related to Tegaserod.

Based on this study and two additional studies with similar findings, the FDA approved tegaserod for up to 12 weeks of treatment for women with constipation-predominant IBS.

What is the recommended dose of tegaserod?

The recommended dose is of tegaserod is 6 mg twice daily for 12 weeks. For optimal results, it should be taken on an empty stomach half an hour before breakfast and dinner.

Are there any precautions when taking tegaserod?

Patients with major liver or kidney disease should not take tegaserod. The safety of tegaserod to the fetus or infant in pregnant or nursing women has not been studied and is unknown. Therefore, tegaserod should be avoided by pregnant or nursing women.

Are there other issues to be considered when using tegaserod?

Even though tegaserod has been used in Europe for some time, and the experience in Europe has shown few side effects, doctors in the US have limited experience because the drug has been recently approved. As with every new FDA-approved medication, doctors in the US need longer-term experience before the safety of tegaserod can be confirmed.

Tegaserod has been approved for relieving constipation, abdominal pain, and bloating in patients with IBS, yet there are many other causes of constipation unrelated to IBS. Accurate diagnosis and careful patient selection is vitally important to ensure that problems other than IBS are not missed.

IBS is a chronic disorder, yet tegaserod has been approved for only 12 weeks of treatment at a time. Until long-term (more than 12 weeks in this case) information on safety and efficacy become available, doctors must decide whether or not to extend treatment beyond 12 weeks.

Though less common than women, men also suffer from IBS, yet tegaserod is approved only for women. Before more data on men become available, doctors must decide whether or not to offer tegaserod to men. I have prescribed tegaserod for three patients; one of them is a man. This man has severe, debilitating, prolonged IBS with constipation that has failed all treatments. I hope it works!

Medical Author: Dennis Lee, M.D.
Medical Editor: Jay W. Marks, M.D.

Last Editorial Review: 10/14/2002