Crofelemer for Functional Diarrhea

Inclusion Criteria: 1. Patient is a man or woman aged 18 to 65 years, inclusive, at Screening. 2. Patient has functional diarrhea defined by the Rome IV criteria as loose (mushy) or watery stools ≥25% and hard or lumpy stools \<25% of bowel movements 3. Patient has had a colonoscopy performed: 1. Within 10 years prior to Prescreening if patient is at least 50 years of age (alternatively, a flexible sigmoidoscopy, double contrast barium enema, or CT colonography within the past 5 years is acceptable \[see recommendations of the American Cancer Society\]) 2. Since the onset (if applicable) of any of the following alarm features for patients of any age (see Spiller and Thompson, 2010 - i.e. Patient has documented weight loss within the past 6 months; Patient has nocturnal symptoms; Patient has a familial history of colon cancer; or patient has blood mixed with their stool (excluding any blood from hemorrhoids). 4. Patient has an average daily stool consistency score (BSS) of ≥5.5 on days without the use of an anti-diarrheal and at least 3 days with a BSS score ≥5 on a 1 to 7 scale over the week prior to randomization. 5. Patient has completed the daily diary on at least 6 of the 7 days during the week prior to randomization AND at least 11 of the 14 days during the 2 weeks prior to randomization. 6. Patient has not used loperamide rescue medication more than 4 days during the screening period. 7. Patient is not planning to change his/her usual diet and lifestyle during the course of the study. 8. Patient is willing to be compliant with study procedures including completing the daily diary during the screening period and throughout the study. 9. Patient must sign an informed consent document before the initiation of any study-related procedures indicating that he or she understands the purpose of and procedures required for the study and is willing to participate in the study. Exclusion Criteria: 1. Patient has a history of inflammatory or immune-mediated GI disorders including inflammatory bowel disease (ie, Crohn's disease, ulcerative colitis, microscopic colitis) and celiac disease. 2. Patient has a predominant symptom of abdominal pain. 3. Patient has a history of diverticulitis within 3 months prior to screening. Patients with a history of diverticulosis are candidates for the study. 4. Patient has a history of intestinal obstruction, stricture, toxic megacolon, GI perforation, fecal impaction, gastric banding, bariatric surgery, adhesions, ischemic colitis, or impaired intestinal circulation (eg, aortoiliac disease). 5. Patient has any of the following surgical history: 1. Any abdominal surgery within the 3 months prior to screening; or 2. Patient has a history of major gastric, hepatic, pancreatic, or intestinal surgery (appendectomy, cholecystectomy, hemorrhoidectomy, or polypectomy greater than 3 months are allowed). For the purposes of this study, laparoscopic surgeries without complication are considered minor and non-exclusionary, provided the condition for which the surgery was performed was not exclusionary. 6. Patient has an unstable renal, hepatic, metabolic, or hematologic condition. 7. Patient has a history of human immunodeficiency virus infection. 8. Patient has a history of DSM-IV-TR-defined substance dependency, excluding nicotine and caffeine, within 2 years prior to Prescreening. 9. Patient has a history of alcohol abuse as defined by DSM-IV-TR, binge drinking as defined by the National Institutes on Alcohol Abuse and Alcoholism, or any medical treatment for alcohol-related co-morbidities, within 5 years prior to Prescreening. Recovered alcoholics who have not consumed alcohol over the 5 years prior to Prescreening are candidates for the study. 10. Patient has current (within 14 days of randomization) or expected use of any narcotic or opioid containing agents, tramadol 11. Patient is unable to swallow solid, oral dosage forms whole with the aid of liquid (patients may not chew, divide, dissolve, or crush the study drug). 12. Patient has received an investigational drug or used an investigational medical device within 30 days prior to randomization. 13. Patient has a known pregnancy or is breastfeeding.