P. Bercik et al., The effect of ammonia on omeprazole-induced reduction of gastric acidity in subjects with Helicobacter pylori infection, AM J GASTRO, 95(4), 2000, pp. 947-955
OBJECTIVE: Omeprazole produces a higher intragastric pH during Helicobacter
pylori (H. pylori) infection than after cure. We tested the hypothesis tha
t this difference is due to the production of ammonia by H. pylori.
METHODS: Gastric acidity and acid output (AO) were measured overnight in 12
subjects, with and without omeprazole, before and 1 and 6 months after cur
e of H. pylori infection. Gastric ammonia ([NH3]), total bile acid ([TBA])
and protein concentrations and plasma omeprazole levels were measured.
RESULTS: During omeprazole, median AO were 0.0 mmol/h before, 0.86 mmol/h (
p = 0.003 vs before cure) at 1 month, and 0.34 mmol/h (p = 0.02) at 6 month
s after cure; median NH3 output was 0.17 mmol/h before, 0.03 mmol/h (p = 0.
002) at 1 month, and 0.02 mmol/h (p = 0.005) at 6 months after cure. AO and
NH3 output were similar 1 and 6 months after cure. When corrected for [NH3
], AO and gastric pH curves were similar before and after cure. Omeprazole
plasma levels increased after cure and gastric [TBA] were unchanged.
CONCLUSIONS: The higher pH observed before cure of H. pylori during omepraz
ole administration is attributable, in large part, to ammonia production. O
ther acid-neutralizing substances and changes in acid secretion may also be
important, but duodenogastric reflux and omeprazole pharmacokinetics are n
ot involved. (C) 2000 by Am. Cell. of Gastroenterology.