OCULAR AVAILABILITY OF GENTAMICIN IN SMALL ANIMALS AFTER TOPICAL ADMINISTRATION OF A CONVENTIONAL EYE DROP SOLUTION AND A NOVEL LONG-ACTING BIOADHESIVE OPHTHALMIC DRUG INSERT

Purpose. Gentamicin eye drop solutions have a short precorneal residence time. The present study investigates the effect of gentamicin using a new long acting delivery Bioadhesive Ophthalmic Insert (BODI) in healthy dogs and rabbits and compares the results with a conventional regimen using an eye drop solution. Methods. In vivo assays were performed on animals after deposition of one BODI and instillations of an eye drop solution. Tear samples were collected over 72 hours and 60 minutes, in the case of inserts and eye drop solution respectively. The gentamicin concentration profiles in tear fluid (determined by a fluorescent polarization immunoassay technique) was individually analyzed, in each animal, in relation with the minimum inhibitory concentration observed in vitro against some bacteria. A non classical pharmacokinetic approach was used for the analysis of the topically applied drug substance, involving two parameters: the efficacy area under the curve (AUC(eff)) and the efficacy time (t(eff)). Results. In the case of the eye drop solution, the AUG,, were higher in dogs (2.80 10(3) - 3.64 10(3) [mu g ml(-1) h]) than in rabbits (0.64 . 10(3) - 0.95 . 10(3) [mu g ml(-1) h]); the t(eff) had a similar behavior: 6-15 [h] in dogs and 2-6 [h] in rabbits. In the case of BODIs, the AUG(eff) and the t(eff) were quite similar between dogs and rabbits: 190 10(3) - 205 10(3) [mu g ml(-1) h] and 70-76 [h], respectively. The AUG(eff) and the t(eff) were always much higher in the case of BODIs than for the eye drop solution both in dogs and rabbits. Conclusions. This study shows that topical administration of gentamicin using BODIs can improve treatment due to the decreasing number of applications while ensuring an effective level of antibiotic in tears controlled by the device.