Effect of lactitol on blood ammonia response to oral glutamine challenge in cirrhotic patients: Evidence for an effect of nonabsorbable disaccharideson small intestine ammonia generation

OBJECTIVE: Nonabsorbable disaccharides are widely used to decrease blood am monia concentration. Their principal mode of action is the modification of pH and bacterial flora in the colon. The aim of the present study was to te st the hypothesis that these drugs may also reduce small intestine ammonia generation. METHODS: Eight male cirrhotics without overt hepatic encephalopathy receive d 20 g of glutamine in 100 mi of water. Venous samples for whole blood ammo nia were taken before, 30 and 60 min after the load. Immediately after the last blood sample the patients were submitted to the following psychometric tests: number connection test, Posner's attention test, and Sternberg para digm. After the first glutamine load, patients were started on lactitol (in itial dose 20 g, three times a day). Once two bowel movements/day were obta ined and maintained for at least 5 days, oral glutamine challenge and psych ometric tests were repeated. RESULTS: Ammonia increased significantly after the glutamine load (from 83 +/- 13 to 164 +/- 30 mu g/dl at 30 min and 210 +/- 29 mu g/dl at 60 min; me an +/-SE; p = 0.006 analysis of variance) but not after glutamine load afte r lactitol treatment (from 77 +/- 17 to Ill +/- 21 mu g/dl and 142 +/- 24 m u g/dl; p = not significant). The peak increment(127 +/- 24 vs 65 +/- 18 mu g/dl; p = 0.008). of ammonia elevation was significantly smaller during la ctitol administration. The patients' psychometric performance after the glu tamine load did not differ significantly after lactitol treatment. CONCLUSIONS: Lactitol reduces the elevation in blood ammonia that follows o ral glutamine challenge. Because enterally administered glutamine is effici ently absorbed in the jejunum and, in part, metabolized to ammonia we sugge st that lactitol affects small intestine ammonia generation probably by sho rtening the residence time of intestinal contents. (C) 1999 by Am. Coil. of Gastroenterology.