Reduction of gastric ammonia by ampicillin in normal and azotemic subjects.

Ampicillin was tested with regards to its capacity to reduce gastric ammonia production in basal and betazole-stimulated gastric secretion. A 7-day course of oral ampicillin (4 g per day) reduced basal gastric ammonia concentration from 5.5 +/- 1.4 to 1.8 +/- 0.3 mM and postbetazole ammonia from 4.7 +/- 0.9 to 1.3 +/- 0.3 mM (P less than 0.01) in 7 control subjects. Similar results were obtained after oral neomycin (4 g per day) or intramuscular ampicillin (4 g per day), each given to a separate group of 7 control subjects. In 5 azotemic patients, oral ampicillin treatment resulted in a reduction of ammonia concentration from 16.3 +/- 4.7 to 3.1 +/- 0.7 mM in basal secretion and from 18.3 +/- 8.1 to 2.3 +/- 0.6 mM in betazole-stimulated gastric juice (P less than 0.01). Antibiotic therapy did not alter volume of gastric secretion. Gastric acidity appeared lower in azotemic patients and increased significantly after treatment, indicating that the higher ammonia content could account for at least part of the hypoacidity. Because ampicillin is active orally as well as parenterally and can be readily used in renal failure, it may be of value for the treatment of hepatic encephalopathy, especially in the azotemic patient in whom neomycin is toxic.