What is the efficacy of the new serotonergic agents in men?
 

Susan Lucak MD: There are two serotonergic medications available for irritable bowel syndrome. First is alosetron, which was introduced on the (U.S.) market in the year 2000. The studies were done with both women and men, but the number of men in those studies was very small and no statistically significant differences could be seen in terms of efficacy in men. So the medication was approved for the treatment of irritable bowel syndrome with diarrhea in women.

Subsequent study done by George Dukes and others has shown that the medication is effective in men, as well. Further studies were done on transit time in men by Camilleri. Again, that study showed that it was efficacious in men. The efficacy, however, is stronger in women. So currently, alosetron has been re-approved by the FDA mainly for women, because the studies in men have not been as strong.

With regards to tegaserod, the phase III trials that were done by Mueller-Lissner have shown, once more, that the medication is more effective in women. However, 90% of study subjects included in the phase III trials were women. So it's very difficult to say for sure whether tegaserod is effective in men.