Sustained reduction of intraocular pressure in humans with the calcium channel blocker verapamil

We investigated the effect of the calcium channel blocker verapamil on intraocular pressure in human volunteers. In the initial trial, 15 subjects with untreated ocular hypertension were tested. After a baseline measurement was obtained with applanation tonometry, a 40-microliter drop of verapamil, 1.25 mg/ml, was instilled in one eye. After 30 minutes, a second reading was taken. In a subsequent trial of 12 untreated ocular hypertensive subjects, the duration of action was determined using the same dose and method of delivery. Results showed that verapamil elicited a mean +/- S.E.M. change in intraocular pressure of -3.8 +/- 0.900 mm Hg in the treated eye, and -1.6 +/- 0.400 mm Hg in the untreated eye. This reduction was statistically different in both eyes (treated eye, P = .0007; untreated eye, P = .005). This decrease in intraocular pressure remained statistically significant when compared to predrug baseline values for up to ten hours.