Noncross-linked collagen discs and cross-linked collagen shields in the delivery of gentamicin to rabbits eyes

Using fluorescent polarization immunoassay, in vitro absorption and elution of gentamicin by noncross-linked collagen discs was measured. This technique was compared with that of cross-linked collagen shields and topical drops to provide adequate gentamicin levels in the cornea and aqueous humor of the rabbit eye. In vitro results showed that the noncross-linked collagen discs absorbed increased gentamicin with prolonged soaking time. All 2-hr presoaked discs completely dissolved within 6 min after being placed in the lower fornix of the rabbit eye. The presoaked discs released most of their gentamicin load within 0.5 hr of elution. Gentamicin levels in the cornea and aqueous humor, using 2-hr presoaked discs, were similar to those obtained with a single drop (P greater than 0.05) of topical solution and significantly lower than those obtained by applying a collagen shield at all intervals (P less than 0.01) and by hourly drops measured at 4- and 6-hr intervals (P less than 0.01). These results suggest that, in their current formulation, the presoaked collagen discs may not be an effective alternative to collagen shields or topical drops for gentamicin delivery because of their rapid dissolution in the eye.