Significant diarrhea (defined as loose or watery stool and or more than three bowel movements daily associated with urgency more than 25% of the days in preceding 3 months) Untreated hypothyroidism Organic or structural disease as the cause of patient's symptoms (stricture or tumor) Diseases that affect bowel transit time (Gastroparesis, short bowel syndrome) Evidence of cathartic colon History of alcohol, laxative abuse or illicit drug use Pregnant or lactating women Planning pregnancy or become pregnant during study period Concomitant use of any medication that could alter gastrointestinal motility (Calcium channel blockers, Narcotics, anticholinergics, calcium and aluminium containing antacids, phenothiazines, ferrous sulfate)