Ocular pharmacokinetics of verapamil in rabbits

Previously, it had been demonstrated that cataract in diabetic rats can be prevented by systemical administration of the calcium channel blocker verapamil. In addition to that, 0.125% verapamil eye drops were found to significantly reduce the intraocular pressure in ocular hypertensive human subjects. The purpose of this study was to investigate the ocular penetration and elimination of verapamil after topical administration of the drug in rabbits. Two drops of a 0.125% aqueous solution of RS-verapamil hydrochloride (corresponding to a total dose of 125 μg RS-verapamil hydrochloride) were administered into the conjunctival sac. Aqueous humor and blood samples were taken at different times after administration and analysed for drug concentration by combined gas chromatography-mass spectroscopy.