Cathartics bulk saline laxatives

Laxatives are used to increase stool frequency and reduce stool viscosity. Even with long-term use, bulk laxatives and pure osmolar laxatives do not predispose patients to formation of a cathartic-type colon and should be the initial agents used for chronic constipation after a structural obstructing lesion has been excluded. Laxatives are also used before radiological, endoscopic, and abdominal surgical procedures such preparations quickly empty the colon of fecal material. Nonabsorbable hyperosmolar solutions or saline laxatives are used for this purpose. Classification and comparison of representative laxatives are provided in Table 40.1. 

C Calcium and iron supplementation are common causes of constipation. Polycarbophil, a bulk-forming laxative, exerts its therapeutic effect by increasing the mass and water content of stool and by speeding transit time in the colon. Cascara sagrada and sennosides are cathartics, which speed colonic transit time and alter water and electrolyte transport across the colonic mucosa. Sodium biphosphonate is a saline cathartic, which increases intestinal peristalsis by osmotic properties. Docusate sodium is a stool... 

Osmotic laxatives (hyperosmolar) are salts or saline products, lactulose, and glycerin. The saline products are composed of sodium or magnesium, and a small amount is systemically absorbed. They pull water into the colon and increase water in the feces to increase bulk, which stimulates peristalsis. Saline cathartics cause a semiformed-to-watery stool depending on dose. However, they are contraindicated for patients who have congestive heart failure. 

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