Determination of azithromycin in gastric biopsy samples.

OBJECTIVES: To measure the concentration of azithromycin in gastric biopsy samples of gastritis patients undergoing Heliobacter pylori eradication treatment 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. pylori. 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 daily 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 occasion of gastroscopic interventions. The gastric samples were subject to analysis of azithromycin, using a highly sensitive and specific HPLC method with electrochemical detection. RESULTS: The median concentrations of azithromycin in gastric tissue amounted to 7.5 microg/g on day 2 and to 9.7 microg/g on day 5 of the treatment. Four days after the end of treatment, median concentrations were still at 3.9 microg/g. In all tissue samples, azithromycin concentrations were well above the MIC for H. pylori (0.25 microg/ml). The well-known tissue affinity of azithromycin was underlined by the lack of detectable levels in gastricjuice. CONCLUSION: The high concentrations of azithromycin observed in gastric tissue of patients with gastritis on a 5-day dosage regimen point to a favorable pharmacokinetic basis for a role of azithromycin as a component of the eradication therapy of Heliobacter pylori.