Inhibitory potency of twice-a-day omeprazole on gastric acidity is enhanced by eradication of H. pylori in duodenal ulcer patients.

The gastric pH-elevating effect of proton pump inhibitors such as omeprazole has been reported to be greater in the presence than in the absence of an H. pylori infection. It is unknown if this effect persists when a higher dose of omeprazole is taken. We undertook both 24-hr pH-metry and 24-hr aspiration studies in 12 H. pylori-positive patients with a history of duodenal ulcer (DU); (1) when not on omeprazole; (2) when on omeprazole 20 mg twice a day for 8 days; (3) two months after eradication of H. pylori and when not on omeprazole; and (4) after eradication of H. pylori and when on omeprazole twice a day. Eradication of H. pylori in DU results in lower mean and median pH; decreased percent pH > or = 3/ > or = 4, and greater median H+ after breakfast, after lunch, and overnight; and omeprazole appears to have less of a pH-elevating effect in the absence than in the presence of an H. pylori infection. The fall in gastric juice NH3 concentration as a result of eradicating H. pylori partially explained the lower pH-elevating effect of omeprazole. The variation in acid inhibitory effect of omeprazole after as compared with before eradication of H. pylori could not be explained by differences; (1) in gastric juice concentrations of IL-1alpha, IL-8, IL-13, or epidermal growth factor; (2) in the fasting or fed total concentration of gastric juice bile acids; (3) in the fasting concentrations or area under-the-curve (AUC) of the gastric H+ concentrations in response to food; or (4) in the pharmacokinetics of omeprazole. The difference in H+ AUC without omeprazole minus with omeprazole was actually greater when compared after versus before eradication of H. pylori. Thus, in DU the pH-elevating potency of omeprazole taken twice a day is greater in the presence than in the absence of an H. pylori infection.