Effect of Topically Applied Iganidipine Dihydrochloride, a Novel Calcium Antagonist, on Optic Nerve Head Circulation in Rabbits

Abstract

Purpose: To study the effect of topically applied iganidipine dihydrochloride (iganidipine), a novel water-soluble calcium channel blocker, on blood flow in the optic nerve head (ONH), intraocular pressure, and systemic blood pressure in rabbits. Methods: After 0.1% iganidipine (20 μL) was instilled into normal eyes, the change in ONH blood flow was measured using a hydrogen gas clearance flowmeter. Iganidipine (0.0001% to 0.1%) was instilled into eyes with impaired ocular circulation before or after the intravitreal injection of endothelin-1, and the change in ONH blood flow was measured. Changes in intraocular pressure and blood pressure after instillation of 0.1% iganidipine were measured. In all experiments, physiological saline was instilled into the contralateral eye as a control. Results: Iganidipine significantly increased the ONH blood flow in normal eyes with the maximum increment of 31.7% at 45 minutes after instillation. Preinstillation of 0.01% and 0.1% iganidipine significantly inhibited the decrease in ONH blood flow in the eyes with impaired circulation. Moreover, ONH blood flow recovered with postinstillation of 0.1% iganidipine. These effects were persistent. Instillation of 0.1% iganidipine did not change either the intraocular pressure or the blood pressure. Conclusion: The instillation of iganidipine persistently increased and maintained the ONH blood flow in rabbit eyes with normal and impaired ocular circulation.