Disclosed is the use of an amount of an extract isolated from the latex of Croton spp. or a Calophyllum spp. which is effective to treat constipation-predominant irritable bowel syndrome (c-IBS) for the manufacture of a medicament for treating c-IBS, wherein said amount is bioequivalent to an orally administered dose of 250 mg per day to 4000 mg per day of crofelemer.
