Determination of azithromycin in gastric biopsy samples

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.

Seven male outpatients, non-smokers, non-alcoholics, aged 25-40 years (mean 32 years), suffering from gastritis with involvement of H. pylori.

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.

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.

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.