Pharmacokinetics of intravitreal vancomycin in normal and infected rabbit eyes

The purpose of this study was to determine the pharmacokinetics governing t he distribution and elimination of intravitreally injected vancomycin in no rmal and infected rabbit eyes. Two groups each of 36 pigmented animals were used. Group 1 served as contro l. In Group 2, experimental endophthalmitis was induced in the right vitreo us by inoculation with Staphylococcus aureus. Once endophthalmitis develope d, a vancomycin solution was injected. Four animals from each group were ki lled at nine time points post-injection, the vitreous and aqueous were remo ved, and blood samples were taken for HPLC analysis. Data analysis was perf ormed using the RSTRIP program. The half-lives were 69 hours in normal vitreous and 14.53 hours in infected vitreous. Therapeutic drug levels were present in the vitreous 84 hours po st-injection in all eyes; they were detected from 2 to 48 hours in normal a queous but at lower levels in the infected ones. Ky and Ca/Cv ratios sugges ted that the primary route of elimination was across the retina and the ant erior chamber in normal eyes, and via the retina in infected eyes. Results indicate that pharmacokinetic parameters change in pathological con ditions, which may help establish better treatment guidelines for endophtha lmitis.