Intravitreal clearance of moxifloxacin

To study the clearance of a single dose of intravitreally injected moxifloxacin in rabbits.

Intravitreal injections of 200 microg/0.1 mL of moxifloxacin were performed in rabbits. Four eyes per time interval after injection (1, 6, 12, 24, 36 hours) and three eyes at 48 hours were enucleated, immediately frozen, and placed at -80 degrees C. Ocular dissection and isolation of frozen vitreous were performed. Antibiotic assays were performed with use of high-performance liquid chromatography.

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 microg/mL 1 hour after injection, which declined to 20.23 +/- 5.85 microg/mL at 6 hours and 1.06 +/- 0.81 microg/mL at 12 hours. The aqueous levels of moxifloxacin showed an exponential decay from 10 microg/mL at 1 hour after intravitreal injection to undetectable levels by 12 hours after injection.

Moxifloxacin clearance from the vitreous is rapid and consistent with previous clearance studies of ciprofloxacin. Given that the injected dose corresponds to several times the minimum inhibitory concentration at which 90% of isolates are inhibited (MIC90) of organisms commonly involved in endophthalmitis, and that therapeutic levels are present up to 12 hours after injection, intravitreal moxifloxacin may have a role in the treatment of endophthalmitis.