Clearance of intravitreal moxifloxacin

PURPOSE. To study the clearance of moxifloxacin after intravitreal injection in rabbits. METHODS. Intravitreal injections of 200 μg/0.1 mL of moxifloxacin were administered to rabbits. Four eyes per time point after injection (1 hour and 6, 12, 24, and 36 hours) and three eyes at 48 hours, respectively, were enucleated and immediately frozen and stored at -80°C. Ocular dissection and isolation of frozen vitreous was performed. Vitreous samples were acquired at the various time intervals after injection. Antibiotic assays were performed with high performance liquid chromatography. RESULTS. The concentration of intravitreal moxifloxacin showed an exponential decay with a half-life of 1.72 hours. The mean vitreous concentration was 120.49 ± 49.23 μg/mL 1 hour after injection, and declined to 20.23 ± 5.85 μg/mL at 6 hours and 1.06 ± 0.81 μg/mL at 12 hours, respectively. CONCLUSIONS. The vitreous concentrations achieved were several orders of magnitude greater than the MIC₉₀ of organisms commonly involved in bacterial endophthalmitis, and therapeutic levels were maintained at 12 hours in uninflamed, phakic rabbit eyes. The pharmacokinetic data suggest that intravitreal moxifloxacin may have a role in the treatment of bacterial endophthalmitis.