The effect of topical diltiazem on the intraocular pressure in betamethasone-induced ocular hypertensive rabbits.

The effect of calcium channel blockers (CCBs) on intraocular pressure (IOP) remains still controversial, although some preliminary reports suggest that these drugs may be effective in the management of ocular hypertension and low-tension glaucoma. The aim of the present work was to assess the effect of topical diltiazem on IOP in an animal model for glaucoma, the betamethasone-induced ocular hypertension in rabbits. IOP was measured with a manometrically calibrated applanation pneumatonograph. Ocular hypertension was produced in 120 rabbits by weekly subconjunctival injection of a betamethasone suspension into the left eye. The experiments examining the ocular actions of diltiazem were carried out in two stages. In the first one, the ability of topical diltiazem to prevent the rise in IOP induced by betamethasone was studied. In a second phase, the effect of topical diltiazem on IOP in betamethasone-induced ocular hypertensive rabbits was assessed. Diltiazem was topically applied once daily for 5 days a week into the left eye. The effect of five different concentrations of diltiazem was evaluated to obtain dose-response curves. Topical diltiazem was found to prevent in a dose-related fashion the betamethasone-induced IOP rise as well as to reduce IOP in rabbits made ocular hypertensive by weekly subconjunctival injection of betamethasone. Unilateral topical administration did not produce a clear effect on IOP in the untreated eye. This is the first report describing the ocular hypotensive action CCBs in animal model for glaucoma. These findings are in agreement with preliminary evidence suggesting that CCBs may have a beneficial effect in human ocular hypertension.