Laxatives (purgatives, aperients) are foods, compounds or drugs taken to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant and saline laxatives are used to evacuate the colon for rectal and/or bowel examinations, and may be supplemented by enemas under certain circumstances. Sufficiently high doses of laxatives may cause diarrhea. Laxatives work to increase the movement of feces along the colon. Some laxatives combine more than one active ingredient.