Effect of Calcium Channel Blockers on Intraocular Pressure in Rabbits

The objective of the study was to evaluate the antiglaucoma effect of calcium channel blockers diltiazem and verapamil. Albino rabbits were used and chronic glaucoma was induced in them using freshly prepared 150 units of alpha–chymotrypsin. 0.1 mL of drug solution was administered topically into the left eye whereas the right served as control. The pressure recording was carried out at 15, 30, 45, 60, 90, 120, 180, 240, 300, 360 and if required at 420 and 480 min after drug instillation. Acute glaucoma was induced using 5% glucose solution administered intravenously, through the marginal ear vein, at a dose of 15 mL/kg body weight. The Intraocular Pressure (IOP) was recorded with a Schiotz-type indentation tonometer, which was previously calibrated by an open manometric calibration procedure. Topical administration of diltiazem (1%) (37.8 ± 0.632456 to 24.48 ± 0.6531) and verapamil (0.125%) (38.95 ± 1.40 to 22.85 ± 0.43) significantly reduced the elevated IOP (>30 mmHg) in alpha chymotrypsin induced chronic glaucoma model and diltiazem (1%) and verapamil (0.125%) prevented acute rise in the intraocular pressure induced by intravenous administration of 5% glucose. Verapamil and diltiazem have IOP lowering effect and can be utilized as potential investigative antiglaucoma drugs.