COLLAGEN SHIELDS IMPREGNATED WITH GENTAMICIN-DEXAMETHASONE AS A POTENTIAL-DRUG DELIVERY DEVICE

We investigated the ability of collagen shields impregnated with genta micin sulfate and dexamethasone to deliver medication into rabbit eyes . We compared the aqueous humor gentamicin and dexamethasone levels de livered by collagen shield and subconjunctival injection therapy at fi ve time points over a ten-hour period, by using a fluorescence polariz ation immunoassay and high-pressure liquid chromatography. Our in vitr o studies showed that impregnated collagen shields released most of th e gentamicin within the first 30 minutes of elution, whereas dexametha sone was released gradually over a ten-hour period. The collagen shiel ds impregnated with gentamicin and dexamethasone produced aqueous gent amicin levels that were significantly lower (P = .014) than those prod uced by subconjunctival injection therapy at 30 minutes and that were comparable to subconjunctival injection therapy at the other time poin ts. Minimum inhibitory concentrations of gentamicin (almost-equal-to 4 mug) were observed in aqueous humor within 30 minutes in rabbits that received subconjunctival injections and at one hour in rabbits treate d with impregnated collagen shields. The impregnated collagen shields produced aqueous dexamethasone levels that were significantly lower (P = .004) than those produced by subconjunctival injection therapy at o ne hour, significantly higher (P = .028) than subconjunctival injectio n therapy at six hours, and comparable to subconjunctival injection th erapy at the other time points. Collagen shield delivery of gentamicin -dexamethasone may be comparable to subconjunctival injections and pro vide an alternative therapy after intraocular surgery.