Azithromycin concentration in rabbits' plasma and posterior segment of the eyes following oral drug administration: a dose-finding study for the application in ocular toxoplasmosis

INTRODUCTION: Azithromycin has been used as an ocular toxoplasmosis alternative treatment due to its pharmacokinetic profiles. However, sufficient concentrations to promote toxoplasmosis eradication is still unknown. This study was aimed to evaluate azithromycin levels in rabbits after three regimens equivalent to human doses for ocular toxoplasmosis. METHODS: Three groups of New Zealand albino rabbits were given one of the following: azithromycin at 26 mg/kg BW daily (Group 1), 26 mg/kg BW every two days (Group 2), and 50 mg/kg BW once weekly (Group 3) for 14 days. Plasma and ocular azithromycin concentrations were examined. RESULTS: Following 14 days, median ratio of plasma maximum azithromycin concentration to the minimum inhibitory concentration for Toxoplasma gondii (C-max/MIC) for Group 1, and 2 were 51.29, 5.33, while Group 3 was undetected. The median azithromycin concentration in the retina-choroid was higher than the MIC in Group 1 (1356.0 ng/ml) and Group 2 (189.0 ng/ml), but not in Group 3. CONCLUSION: Azithromycin administered orally at the dose of 26 mg/kg BW daily or 26 mg/kg BW every two days resulted a sufficient criteria of C-max/MIC as well as retina-choroid concentration needed for its parasiticidal activity. However, well-conducted clinical trial is warranted to support its therapeutic potential in ocular toxoplasmosis.