Determination of azithromycin in gastric biopsy samples

Objectives: To measure the concentration of azithromycin in gastric biopsy samples of gastritis patients undergoing Helicobacter pylori eradication tr eatment with azithromycin as one antibiotic constituent of the medication. Patients: Seven male outpatients, non-smokers, non-alcoholics, aged 25 - 40 years (mean 32 years), suffering from gastritis with involvement of H, pyl ori. Methods: The patients received a 5-day treatment with azithromycin (1 x 500 mg on day 1 and 1 x 250 mg on days 2 - 5), 40 mg pantoprazole once da ily and 2 x 400 mg metronidazole once daily. Samples of gastric tissue were obtained from 5 patients and of gastric juice from 2 patients, at the occa sion of gastroscopic interventions. The gastric samples were subject to ana lysis of azithromycin, using a highly sensitive and specific HPLC method wi th electrochemical detection. Results: The median concentrations of azithro mycin in gastric tissue amounted to 7.5 mu g/g on day 2 and to 9.7 mu g/g o n day 5 of the treatment. Four days after the end of treatment, median conc entrations were still at 3.9 mu g/g. In all tissue samples, azithromycin co ncentrations were well above the MIC for H. pylori (0.25 mu g/ml). The well -known tissue affinity of azithromycin was underlined by the lack of detect able levels in gastric juice. Conclusion: The high concentrations of azithr omycin observed in gastric tissue of patients with gastritis on a 5-day dos age regimen point to a favorable pharmacokinetic basis for a role of azithr omycin as a component of the eradication therapy of Heliobacter pylori.