Kinetics and tolerability of intravitreal pefloxacin in rabbits

In the treatment of patients with bacterial endophthalmitis, the intravitreal administration of antibiotics is suitable for induction therapy since it provides immediate high concentrations in the vitreous humor. Pefloxacin has been shown to have good intraocular penetration when given systemically. In order to extend the potential routes of administration of this agent, we have assessed the kinetics and toxicity of pefloxacin in rabbit phakic eyes following intravitreal instillation. Kinetic parameters were determined for 12 albino and 12 pigmented rabbits after a single injection of 80 micrograms. Pefloxacin was undetectable in the aqueous humor but high concentrations were found in the chorioretina. The vitreal half-life was short (3 h). These results were consistent with posterior elimination via the chorioretina. Pefloxacin concentrations in the iris and chorioretina of pigmented rabbits were two-fold greater than those in albino rabbits, probably because of binding to the pigmentary apparatus. Toxicity studies, including ophthalmological and histopathological investigations, identified a maximum non-toxic dosage of 400 micrograms. Intravitreal pefloxacin may therefore be suitable for induction therapy in patients with endophthalmitis, although further studies in primates are required to confirm the efficacy and tolerability of this route of administration.