Effects of drug vehicles on ocular uptake of tetracycline

Varying concentrations of tetracycline hydrochloride were topically applied to the rabbit eye in several ophthalmic vehicles. The antibiotic levels in the corneal epithelium, aqueous humor, and lens were markedly elevated by increasing the drug concentration and the drug contact time with the eye. The ocular levels of tetracycline were increased by the vehicle in this ascending order: isotonic saline, 1.4% polyvinyl alcohol, 1% alpha-methylcellulose, and a 6:4 mixture of white petrolatum-mineral oil ointment. Tetracycline hydrochloride as a 2.0% suspension in ointment produced anterior chamber and corneal concentrations for several hours in the range of bacteriostasis for many gram-negative bacteria that occasionally invade the eye.