[Lactulose and its derivatives--treatment of hepatic encephalopathy and other possible indications for its use]

Lactulose and lactitol, the synthetic compounds of lactose, are poorly absorbed from the small intestine, and both are almost exclusively metabolized by the bacterial flora of the colon. These disaccharides shorten the small bowel transit time mechanically and lower the pH of the bowel, both by their osmotic effects and by the acidic pH of their metabolites. Lactulose and lactitol diminish the absorption of ammonia and metabolites of other toxic proteins by two distinct mechanisms; by exerting a cathartic effect and by suppressing the dissociation of ammonia. Lactulose and lactitol are the classical therapy of choice for the treatment of hepatic encephalopathy since 1964 and since 1982, respectively. Another indication is, the treatment of constipation. Because lactulose decreases the concentration of cholic acid and may prevent its absorption, the drug was recently suggested to be successful for the prevention of recurrence of cholesterol stone formation, and to be useful as an anticarcinogenic agent.