The effect of ammonia on omeprazole-induced reduction of gastric acidity in subjects with Helicobacter pylori infection

Am J Gastroenterol. 2000 Apr;95(4):947-55. doi: 10.1111/j.1572-0241.2000.01983.x.


Objective: Omeprazole produces a higher intragastric pH during Helicobacter pylori (H. pylori) infection than after cure. We tested the hypothesis that 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 cure 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 months 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 omeprazole administration is attributable, in large part, to ammonia production. Other acid-neutralizing substances and changes in acid secretion may also be important, but duodenogastric reflux and omeprazole pharmacokinetics are not involved.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Ammonia / metabolism*
  • Anti-Ulcer Agents / adverse effects
  • Anti-Ulcer Agents / therapeutic use*
  • Female
  • Follow-Up Studies
  • Gastric Acidity Determination*
  • Gastritis / drug therapy*
  • Gastritis / microbiology
  • Helicobacter Infections / drug therapy*
  • Helicobacter Infections / microbiology
  • Helicobacter pylori / drug effects*
  • Helicobacter pylori / metabolism
  • Humans
  • Hydrogen-Ion Concentration
  • Male
  • Middle Aged
  • Omeprazole / adverse effects
  • Omeprazole / therapeutic use*


  • Anti-Ulcer Agents
  • Ammonia
  • Omeprazole