Level 1: Likely reliable evidence

A randomized, placebo-controlled trial of 2,660 women found that tegaserod (Zelnorm) was effective for initial treatment and during recurrence of irritable bowel syndrome (IBS) flares (Gut. 2005;54:1707-1713). The women, who had constipation-predominant IBS, were randomized to receive oral tegaserod 6 mg twice daily vs. placebo for one month. Symptom relief occurred in 33.7% of women taking tegaserod vs. 24.2% taking placebo (P <0.0001, NNT 11), and 31.3% vs. 22.1% had relief of abdominal pain or discomfort (P <.0001, NNT 11).

Additionally, 1,191 participants who had at least partial response with tegaserod and had symptom recurrence off treatment were randomized to tegaserod 6 mg twice daily vs. placebo for one more month. Relief of IBS symptoms occurred in 44.9% of the treatment group vs. 28.7% of the placebo group (P <.0001, NNT 7), and 42.4% vs. 27.1% had relief of abdominal pain or discomfort (P <.0001, NNT 7).


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In order to maintain blinding of the overall study, 208 participants, who had at least a partial response to placebo, were “mock randomized” to receive tegaserod as well. In this group, 41.8% had relief of IBS symptoms and 36.5% had relief of abdominal pain or discomfort.