lactulose /lak″tyəlōs/ , a nonabsorbable synthetic disaccharide, 4-0-beta-d-galactopyranosyl-D-fructose, C12H22O11. It is hydrolyzed in the colon by bacteria primarily to lactic acid and small amounts of formic and acetic acids, which results in increased osmotic pressure and acidification of the colonic contents. It is used as a cathartic in chronic constipation. Because the acidification causes ammonia to be removed from the blood to form ammonium ion, it is also used in the treatment of hepatic coma. Its ability to increase fecal water content, however, may also cause diarrhea.
