LACTULOSE, DISACCHARIDES AND COLONIC FLORA - CLINICAL CONSEQUENCES

Lactulose is one of the most frequently utilised agents in the treatme nt of constipation and hepatic encephalopathy because of its efficacy and good safety profile. The key to understanding the possible modes o f action by which lactulose achieves its therapeutic effects in these disorders lies in certain pharmacological phenomena: (a) lactulose is a synthetic disaccharide that does not occur naturally; (b) there is n o disaccharidase on the microvillus membrane of enterocytes in the hum an small intestine that hydrolyses lactulose; and (c) lactulose is not absorbed from the small intestine. Thus, the primary site of action i s the colon in which lactulose is readily fermented by the colonic bac terial flora with the production of short-chain fatty acids and Variou s gases. The purpose of this review is to focus on some pertinent basi c aspects of the clinical pharmacology of lactulose and to discuss the possible mechanisms by which lactulose benefits patients with constip ation and hepatic encephalopathy.