Objective: To assess azithromycin levels in human serum, aqueous humor, tear fluid, and conjunctival tissue specimens after administration of a single 1-g oral dose of azithromycin. Methods: Sixty patients undergoing cataract surgery were included in this analysis. Serum, aqueous, and tear specimens were collected 3, 6, and 12 hours and 1, 2, 3, and 4 days after azithromycin administration. Conjunctival tissue biopsy specimens were collected 1, 2, 3, 4, 6, 8, 10, 12, and 14 days after azithromycin administration. All specimens were subjected to analysis by high-performance liquid chromatography-mass spectrometry. Results: Azithromycin concentration ranges during the specified sampling times were as follows: serum, 21 to 974 ng/mL; tear, 82 to 2892 ng/mL; aqueous, 10 to 69 ng/mL; and conjunctival, 0.7 to 32 μg/g. Levels above the 90% minimal inhibitory concentration (MIC90) for Chlamydia trachomatis were detected after 4 days in all tear samples and after 14 days in all conjunctival tissue specimens following oral azithromycin administration. Conclusion: We demonstrated prolonged high levels of azithromycin in drug-targeted ocular tissue. Prolonged high concentrations of azithromycin in conjunctival tissue make this drug suitable for treatment of conjunctivitis caused by chlamydiae and other susceptible organisms.
