Gender-related differences in slowing colonic transit by a 5-HT3 antagonist in subjects with diarrhea-predominant irritable bowel syndrome

To evaluate the influence of gender on the effect of a 5-HT3 antagonist, alosetron, 1 mg b.i.d., on GI and colonic transit in D-IBS.Thirty patients (15 male, 15 female) with D-IBS received 1 mg b.i.d. alosetron for 6 wk. Transit was measured by scintigraphy at baseline and at the end of treatment.Alosetron, 1 mg b.i.d., significantly retarded small bowel and, proximal and overall colonic transit in the 30 patients with D-IBS. The effect of alosetron on the primary endpoint, colonic geometric center at 24 h, was significantly greater in females than in males (p < 0.05). However, two females showed no slowing of colonic transit on treatment. Among male patients, two of 15 had a slowing of colonic transit at 24 h that was greater than the mean change in female patients, suggesting responsiveness to alosetron among a subgroup of males.A 5-HT3 antagonist, alosetron, significantly retards small intestinal and colonic transit in diarrhea-predominant IBS patients, with significantly greater female to male responsiveness. Gender partly contributes to differences in the serotonergic control of intestinal and colonic transit in patients with D-IBS.