Elevation of intraocular pressure by calcium channel blockers

Topical administration of three different calcium channel blockers (verapamil hydrochloride, diltiazem hydrochloride, or nifedipine) increased intraocular pressure transiently in rabbits. Outflow facility and episcleral venous pressure were unchanged. Aqueous humor flow seemed to be increased 30 minutes after topical application of verapamil when estimated by the Goldmann equation or by changes in anterior chamber fluorescein-labeled dextran concentration. However, aqueous humor ascorbate concentrations and turnover of radioactive iodide did not differ from that in the untreated eye. Ocular blood volume was found to be increased after topical application of verapamil, which suggested vascular changes as a possible mechanism for the induced increase in IOP. Topical verapamil raised IOP in healthy human volunteers, but the elevation was less than observed in rabbits. Single oral doses of verapamil in rabbits or human beings had no effect on IOP.