Effects of alosetron on gastrointestinal transit time and rectal sensationin patients with irritable bowel syndrome

Background: Alosetron, a 5-HT3-receptor antagonist, relieves abdominal pain and improves bowel function in non-constipated, female patients with irrit able bowel syndrome. 5-HT3 antagonists delay colonic transit, increase colo nic compliance, and increase small intestinal water absorption. Aim: To evaluate the effects of alosetron on gastrointestinal and colonic t ransit, rectal compliance and rectal sensation in irritable bowel syndrome. Methods: A double-blind, placebo-controlled, two-dose study of alosetron wa s performed in 25 non-constipated irritable bowel syndrome patients, with p aired studies before and after 4 weeks of treatment with placebo (n=5), 1 m g alosetron (n=10) or 4 mg (n=10) alosetron b.d. Gastrointestinal and colon ic transit were measured by scintigraphy. Rectal compliance and sensation w ere assessed by rectal balloon distention with a barostat. Results: There was a trend (P=0.06) for 1 mg alosetron to increase rectal c ompliance (median pressure at half maximum volume 11 mmHg after alosetron v s. 15.6 mmHg before alosetron). The 1 mg b.d. alosetron dose non-significan tly retarded proximal colonic transit. Alosetron and placebo reduced sensor y scores relative to baseline values; none of the changes induced by aloset ron was significant relative to placebo. Conclusions: Alosetron had no significant effect on gastrointestinal transi t or rectal sensory and motor mechanisms in non-constipated irritable bowel syndrome patients in this study. Alosetron's effects on colonic sensorimot or function and central sensory mechanisms deserve further evaluation.