Background: The antisecretory effect of omeprazole on intragastric pH is decreased in the absence of Helicobacter pylori. Aim: To investigate the effect of H. pylori eradication on intragastric pH during lansoprazole or ranitidine dosing in 41 asymptomatic H. pylori-positive subjects. Method: Two groups of healthy H. pylori-positive volunteers were investigated. One group was dosed with lansoprazole 30 mg at 08.00 hours for at least 8 days, before and after 2 weeks of placebo-controlled double-blind eradication therapy using ranitidine bismuth citrate 400 mg b.d. and clarithromycin 500 mg b.d. The other group was dosed with ranitidine 300 mg at 23.00 hours for at least 8 days using the same trial design. An upper endoscopy was performed to establish H. pylori status by rapid urease test, culture and histology before both periods of dosing. Twenty-four hour intragastric pH recording was performed on the final day of all periods of dosing. Results: H. pylori eradication significantly decreased the intragastric pH reached during lansoprazole treatment throughout all periods of the day. Intragastric pH during ranitidine treatment was not affected by H. pylori eradication, except for the late-night period. Conclusion: H. pylori eradication has a more pronounced effect on the acid-inhibiting properties of lansoprazole than on those of ranitidine.,
Alimentary Pharmacology and Therapeutics

Van Herwaarden, M.A. (M. A.), Samsom, M., Van Nispen, C.H.M. (C. H M), Mulder, P., & Smout, A. J. P. M. (1999). The effect of Helicobacter pylori eradication on intragastric pH during dosing with lansoprazole or ranitidine. Alimentary Pharmacology and Therapeutics, 13(6), 731–740. doi:10.1046/j.1365-2036.1999.00531.x