Background & Aims Previous studies have indicated that serotonin-3-receptor antagonists might have a sex-specific effect in patients with irritable bowel syndrome with diarrhea (IBS-D). Alosetron has been approved for the treatment of only women, and ramosetron has been approved for the treatment for only men. We performed a randomized, placebo-controlled, phase 3 study to determine whether ramosetron reduces symptoms of IBS-D in women. Methods We performed a prospective study of 576 female outpatients with IBS-D (according to the Rome III criteria), from February 2013 through February 2014, at 70 academic Gastroenterology Departments in Japan. After a 1-week baseline period, subjects received either 2.5 μg ramosetron (n = 292) or placebo (n = 284) once daily for 12 weeks. Primary end points were the monthly rates of response for relief from overall IBS symptoms and increased stool consistency at the last evaluation point. Quality of life (QOL) also was quantified. Results A significantly higher proportion of patients given ramosetron reported global improvement (50.7%; 95% confidence interval [CI], 44.8-56.6) than patients given placebo (32.0%; 95% CI, 26.7-37.8) - a difference of 18.6% (95% CI, 10.7-26.5; P <.001). The relative risk was 1.58 (95% CI, 1.29-1.94) and the number needed to treat was 6 (95% CI, 4-10). A significantly higher proportion of patients in the ramosetron group reported increased stool consistency (40.8%; 95% CI, 35.1%-46.6%) than in the placebo group (24.3%; 95% CI, 19.4%-29.7%) - a difference of 16.5% (95% CI, 8.9%-24.0%; P <.001). Patients receiving ramosetron had significant reductions in abdominal pain and discomfort (P =.001) and greater improvement in QOL (P =.002) compared with placebo. Ramosetron induced constipation in 11.0% of patients. Conclusions In a randomized, placebo-controlled study of 576 women with IBS-D, 2.5 μg ramosetron per day reduced symptoms and increased stool consistency and QOL. Clinicaltrials.gov no: NCT01870895.
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