Collagen Shields Delivery of Netilmicin: A Study of Ocular Pharmacokinetics

Abstract

Collagen shields have been used as therapeutic contact lenses to promote corneal epithelial healing and to deliver hydro-soluble drugs. In albino rabbits, we studied the ocular pharmacokinetics of netilmicin, an aminoglycoside antibiotic, released by a 24-hour collagen shield immersed for 10 min in commercially available eye solution of netilmicin, at the standard concentration of 3 mg/ml. The animals were sacrificed after 0.5,1, 6 and 18 h. The antibiotic concentrations were measured by the microbiological method. The drug levels remained above the MIC for the usual pathogens for 18 h in the cornea and for 6 h in the aqueous humor. In the iris and ciliary body the peak concentration was reached 1 h after shield application, netilmicin concentration decreased thereafter rapidly. The lens and the vitreous did not appear to be permeated by the drug. In the conjunctiva, drug concentrations were low, showing a negligible lateral diffusion of netilmicin released by shields. In conclusion, our findings show, that if the collagen shields are used as delivery systems, a very concentrated drug solution is not required to obtain high and persistent levels of netilmicin in cornea.