Purgatives colon-irritant

Indications for colon-irritant purgatives are the prevention of straining at stool following surgery, myocardial infarction, or stroke and provision of relief in painful diseases of the anus, e.g., fissure, hemorrhoids. 

In the colon, semifluid material entering from the small bowel is thickened by absorption of water and salts (from about 1000 to 150 mL/d). If, due to the action of an irritant purgative, the colon empties prematurely, an enteral loss of NaCl, KCl and water will be incurred. To forestall depletion of NaCl and water, the body responds with an increased release of aldosterone (p. Ltillmann, Color Atlas of Pharmacology... 

The interval between natural stool evacuations depends on the speed with which this colon segment is refilled. A large-bowel irritant purgative clears out the entire colon. 

This oil is a potent stimulant laxative. It is hydrolyzed in the upper small intestine to ricinoleic acid, a local irritant that stimulates intestinal motility. Formerly used as a purgative to clean the colon before procedures, it is now seldom used. 

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