Ibodutant for Relief of Irritable Bowel Syndrome With Diarrhoea (IBS-D)

Inclusion Criteria: At start of the run-in period: * Male or female patients aged 18 - 70 years with a clinical diagnosis of IBS-D according to the Rome III criteria: * Recurrent abdominal pain/discomfort for at least 3 days per month in the last 3 months associated with at least 2 of the following characteristics: 1. improvement with defecation; 2. onset associated with a change in the frequency of stool; 3. onset associated with a change in form (appearance) of stool. * Symptom-onset at least 6 months prior to diagnosis. * Loose/watery stools at least 25% of the time in the last 3 months AND hard/lumpy stools less than 25% of the time in the last 3 months. * More than 3 bowel movements per day at least 25% of the time in the last 3 months. * For patients older than 50 years OR patients with positive family history of colorectal cancer: Normal results from colonoscopy or flexible sigmoidoscopy. * Mentally competent, able to give written informed consent. * For women of childbearing potential: Use of a highly effective contraceptive method throughout the entire study period and up to 30 days post-treatment. * Normal physical examination or without clinically relevant abnormalities. At randomisation: -Confirmation of IBS-D severity in terms of bowel movement frequency and abdominal pain intensity along the 2-week run-in period. Exclusion criteria: * Organic abnormalities of the gastrointestinal tract, including history of colonic or major abdominal surgery. * History of gluten enteropathy. * Lactose intolerance as assessed by response to diet. * History of positive tests for ova or parasites, or occult blood in the stool. * Previous diagnosis of diabetes mellitus (either type 1 or 2). * Unstable medical condition. * Major psychiatric, neurological, or cardiovascular disorders, or uncontrolled metabolic disease. * Relevant changes in dietary habits, lifestyle, or exercise regimen in the previous 2 months. * Use of concurrent medication with drugs known to interfere with gastro-intestinal motility or sensitivity. * Pregnancy or breastfeeding.