LACTULOSE - A MULTIFACETED SUBSTANCE

Lactulose is therapeutically used in hepatic encephalopathy, constipat ion, and salmonellosis. This semisynthetic disaccharide is neither met abolized nor absorbed in the normal small intestines. Comparable to pl ant-polysaccharides lactulose is bacterially fermented in the colon to short chain fatty acids and gases. Major consequences are a drop in p H and a change in composition and metabolic activity of the colonic fl ora. These and other, potential effects suggest complex mechanisms of action of lactulose, with the potential for additional indications in diagnosis and therapy. The use of lactulose as substrate for the H-2-b reath-test is well known as a means for the measurement of orocecal tr ansit time and as test for small intestinal bacterial overgrowth. An e xtension of the diagnostic potential is given by the assessment of the permeability in diffuse intestinal disease with combined disaccharide /monosaccharide test solutions, especially in Crohn's disease. Explana tions for positive effects in the prophylaxis of cholesterol-gallstone s, in the therapy of hypercholesterolemia and in the prevention of col orectal adenoma and carcinoma can be found in changes in lipid- and bi le acid metabolism found after lactulose ingestion. Lactulose may lead to an improved glucose-tolerance in parallel to fibre and acarbose ef fects which involve several mechanisms of carbohydrate metabolism. Lac tulose presumably reduces pathogenic bacteria in favor of the health p romoting bifidusflora; also, production and absorption of endotoxines may be reduced; this suggest that lactulose may have therapeutic effec ts on both infectious and idiopathic inflammatory bowel diseases. Nume rous studies with interesting but not as yet convincingly documented c linical relevance suggest that the many effects of lactulose may be in teresting subjects for future research.