Efficacy, Safety and Tolerability of DNK333 (25 mg Bid) in Women With Diarrhea-predominant Irritable Bowel Syndrome (IBS-D)

Inclusion criteria: * Women of 18 - 65 years of age with IBS-D as defined by the Rome II criteria. * The Rome II criteria is a system used for diagnosing functional gastrointestinal disorders such as irritable bowel syndrome. It involves completing of a questionnaire about gastrointestinal symptoms. * Patients who are 50 years of age and older must have had a colonoscopy OR a flexible sigmoidoscopy plus a double-contrast barium enema within the past 5 years, which demonstrated no clinically significant findings. * Clinically significant findings may include but are not limited to malignant tumors, multiple (≥3) or advanced adenomas, inflammatory bowel disease, diverticulitis, ischaemic colitis, lymphocytic colitis, or collagenous colitis. * Patients must report ≥ 3 days with IBS-related abdominal pain/discomfort plus at least 3 days of 2 or more of the following events during the baseline period: * ≥ 3 bowel movements/day * Bowel urgency * Loose or watery stool Exclusion Criteria: * Patients who answer "yes" to either or both of the two weekly satisfaction questions during the baseline period. The questions are: (1) Over the past week did you have satisfactory relief of your IBS-related abdominal pain/discomfort? (2) Over the last week did you have satisfactory relief of your overall IBS-D symptoms? * Patients with hard or lumpy stools for more than one day during the baseline period. * Lactose intolerant patients relieved on a lactose free diet. * Use of antidepressants (tricyclic, SSRI etc), opioid analgesic drugs or drugs specifically affecting bowel motility during the course of the trial. * Women of child-bearing potential who do not use an acceptable methods of contraception. * Pregnant or nursing (lactating) women. Other protocol-defined inclusion/exclusion criteria may apply.