['The acid inhibitory effect of proton pump inhibitors is reported to be greater in the presence than in the absence of an H. pylori infection. This study was undertaken to test the hypothesis that the acid inhibitory effect of omeprazole given twice a day is greater in H. pylori infected healthy volunteers than in the same individuals following eradication because of differences in the pharmacodynamics of omeprazole, greater duodenogastric reflux, the effects of ammonia produced by the H. pylori, or lower gastric juice concentrations of selected cytokines, which may inhibit gastric acid secretion.', 'We undertook 24-hour pH-metry in 12 H. pylori-positive healthy volunteers: (1) when on no omeprazole; (2) when on omeprazole 20 mg bid for 8 days; (3) 2 months after eradication of H. pylori and when on no omeprazole; and (4) after eradication of H. pylori and when on omeprazole 20 mg twice a day.', "In subjects given omeprazole, eradication of H. pylori reduced pH and percentage pH >or= 3, as well as increasing the area under the H+ concentration-time curve. These differences were not due to alterations in (1) gastric juice concentrations of IL-1alpha, IL-8, IL-13, epidermal growth factor, or bile acids; (2) serum gastrin concentrations; or (3) the pharmacokinetics of omeprazole. There was no change in the difference in the H+ concentration-time curve 'without omeprazole' minus 'with omeprazole', when comparing 'after' versus 'before' eradication of H. pylori."] Is acid inhibitory potency of twice a day omeprazole affected by eradication of Helicobacter pylori in healthy volunteers?