REDUCED AMOXICILLIN UPTAKE INTO HUMAN GASTRIC-MUCOSA WHEN GASTRIC-JUICE PH IS HIGH

Amoxicillin when administered with gastric acid suppressors has been s hown to be effective in eradication of Helicobacter pylori in 50 to 80 % of subjects, The aim of this investigator-blind crossover study was to determine if gastric mucosal amoxicillin uptake was affected by inc reasing gastric juice pH, Fifteen male subjects (7 H. pylori positive and 8 H. pylori negative) were randomized to receive 150 mg of ranitid ine twice a day, 300 mg of ranitidine twice a day, or no drug for 2 da ys prior to upper endoscopy, The last dose of ranitidine was given 60 min prior to upper endoscopy, and amoxicillin (500 mg) was given 30 mi n prior to upper endoscopy. The amoxicillin concentrations in mucosal biopsy samples, gastric juice, and serum were determined by a standard microbiological bioassay technique. Mean amoxicillin levels were grea ter in samples of antrum, fundus, and duodenum for volunteers who rece ived no ranitidine than in those receiving 300 mg of ranitidine (P < 0 .05) and those receiving 150 mg of ranitidine (P < 0.05 except for fun dus), Amoxicillin levels in the antrum, fundus, and duodenum were nega tively correlated with gastric juice pH (P < 0.005 for antrum; P < 0.0 01 for fundus and duodenum), There was no correlation between gastric juice pH and amoxicillin levels in either gastric juice or serum, The amoxicillin concentration in gastric juice was significantly higher wi th 300 mg of ranitidine than with no ranitidine (P < 0.05), Thus, lowe r gastric juice pH is associated with a higher rate of mucosal uptake of amoxicillin.