 Provided the patient has been stable for eight weeks prior to their baseline visit, they will be allowed to take the following medications: drugs that inhibit gastric secretion histamine blockers, proton pump inhibitors, benzodiazepines and Imidazopyridines short acting, nonbenzodiazepine hypnotics for sleep dose must be consistent with the use of a sleep agent aspirin at a cardiovascular prophylactic dose 75-150 mgday and paracetamol. Antidepressants for non-IBS symptoms are allowed. Loperamide will be permitted as a rescue for diarrhea only when patients are experiencing at least 3 liquid or soft stools in one day. However, Loperamide is prohibited during the two week screening period. 