Transfer of metronidazole to gastric juice: Impact of Helicobacter pylori infection and omeprazole

Background: The effects of Helicobacter pylori infection associated with in hibition of gastric acid secretion on the distribution of medications used for H, pylori eradication are poorly understood. The aim of this study was to investigate the effects of a 7-day administration of 20 mg omeprazole on the transfer of metronidazole from plasma to the gastric juice of individu als with and without H, pylori infection. Methods: Fourteen H. pylori-posit ive and 14 H. pylori-negative male volunteers were enrolled in a study with an open, randomized, two-period crossover design with a 21-day washout per iod between phases. Plasma, salivary, and gastric juice concentrations of m etronidazole in subjects with and without omeprazole treatment were measure d with reversed-phase high-performance liquid chromatography/liquid chromat ography. Results: Metronidazole peak concentration (C-max) was similar in p lasma and saliva and was approximate to threefold higher in gastric juice i n all groups. Omeprazole treatment increased gastric pH and did not affect metronidazole C-max or the time required for this to be reached (t(max)) in plasma, saliva, or gastric juice. However, omeprazole significantly reduce d metronidazole transfer from plasma to gastric juice in H, pylori-positive but not H. pylori-negative subjects, as shown by statistical analysis of A UC(0-2h). Conclusion: Short-term treatment with omeprazole in H. pylori- po sitive volunteers reduces the amount of metronidazole transferred from plas ma to gastric juice. This seems to occur in a pH-independent form.