Studies with lactulose (galactose-fructose) and sorbitol indicate that they reduce neurologic abnormalities of hepatic encephalopathy. Nine patients greatly incapacitated by encephalopathy after portacaval shunting were able to continue relatively normal day-to-day living for 6 to 20 months without need for hospitalization because of neurologic symptoms. Sorbitol, a relatively inert sugar administered in a double blind prospective study was often as beneficial as lactulose. The mechanism for reducing neurologic symptoms is believed due to decreased absorption of ammonium and other nitrogen-containing compounds from the colon by the cleansing action of catharsis and lowering of the colon pH.
Brown H, Trey C, McDermott WV. Lactulose Treatment of Hepatic Encephalopathy in Outpatients. Arch Surg. 1971;102(1):25-27. doi:10.1001/archsurg.1971.01350010027006