The effect of ammonia on omeprazole-induced reduction of gastric acidity in subjects with Helicobacter pylori infection.
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.
Bercík
P
P
Division of Gastroenterology, CHUV, Lausanne, Switzerland.
Verdú
E F
EF
Armstrong
D
D
Idström
J P
JP
Cederberg
C
C
Markert
M
M
Crabtree
J E
JE
Stolte
M
M
Blum
A L
AL
D000328:Adult; D000641:Ammonia / Q000378:metabolism*; D000897:Anti-Ulcer Agents / Q000009:adverse effects / Q000627:therapeutic use*; D005260:Female; D005500:Follow-Up Studies; D005745:Gastric Acidity Determination; D005756:Gastritis / Q000188:drug therapy* / Q000382:microbiology; D016481:Helicobacter Infections / Q000188:drug therapy* / Q000382:microbiology; D016480:Helicobacter pylori / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D009853:Omeprazole / Q000009:adverse effects / Q000627:therapeutic use*
D000897:Anti-Ulcer Agents; D000641:Ammonia; D009853:Omeprazole