A randomized, double-blind, placebo-controlled clinical trial of the effectiveness of the novel serotonin type 3 receptor antagonist ramosetron in both male and female Japanese patients with diarrhea-predominant irritable bowel syndrome.

Objective: Irritable bowel syndrome is characterized by abdominal discomfort and/or pain associated with altered bowel habits. The neurotransmitter serotonin and serotonin type 3 receptors that are extensively distributed on enteric neurons in the human gastrointestinal tract play a role in increasing the sensation of pain and affecting bowel habits in patients with irritable bowel syndrome. The aim of this study was to evaluate the efficacy and safety of the serotonin type 3 receptor antagonist ramosetron hydrochloride in Japanese patients with diarrhea-predominant irritable bowel syndrome.
Material and Methods: In a double-blind, placebo-controlled, parallel group-comparative study with a 1-week run-in period, 539 patients with diarrhea-predominant irritable bowel syndrome meeting the Rome II diagnostic criteria received either 5 microg ramosetron hydrochloride (n=270) or placebo (n=269) once daily for 12 weeks.
Results: Forty-seven percent of ramosetron hydrochloride-treated patients were monthly responders in the primary end-point, "Patient-reported global assessment of relief of irritable bowel syndrome symptoms", compared with 27% for placebos (p<0.001). The most frequently reported adverse event in the ramosetron hydrochloride-treated group compared with the placebo group was hard stool.
Conclusions: Ramosetron hydrochloride 5 microg once daily is effective and well tolerated in the treatment of abdominal pain, discomfort and bowel habits in patients with diarrhea-predominant irritable bowel syndrome.