Helicobacter pylori infection potentiates the inhibition of gastric acid secretion by omeprazole

Abstract

BACKGROUNDOmeprazole has a greater intragastric pH elevating effect in Helicobacter pylori positive than negative subjects. Ammonia production byH pylori has been suggested as a probable mechanism.AIMSTo assess the effect ofH pylori status on gastric acid secretion during omeprazole treatment, and to examine the possible role of ammonia neutralisation of intragastric acid in increased omeprazole efficacy in infected subjects.METHODSTwentyH pylori positive and 12H pylori negative healthy volunteers were examined before and six to eight weeks after commencing omeprazole 40 mg/day. On both occasions plasma gastrin and acid output were measured basally and in response to increasing doses of gastrin 17 (G-17). Gastric juice ammonium concentrations were also measured.RESULTSPrior to omeprazole, measurements were similar in the H pyloripositive and negative subjects. During omeprazole, median basal intragastric pH was higher in the H pyloripositive (7.95) versus negative (3.75) subjects (p<0.002). During omeprazole basal, submaximal (180 pmol/kg/h G-17), and maximal acid outputs (800 pmol/kg/h G-17) were lower in H pylori positive subjects (0.0, 3.6, 6.0 mmol/h respectively) versus negative subjects (0.3, 14.2, 18.6 mmol/h) (p<0.03 for each). This effect was not explained by neutralisation by ammonia.CONCLUSIONThe presence ofH pylori infection leads to a more profound suppression of acid secretion during omeprazole treatment. The effect cannot be explained by neutralisation of intragastric acid by bacterial ammonia production and its precise mechanism has to be explained.