Effects of lomerizine, a calcium channel antagonist, on retinal and optic nerve head circulation in rabbits and humans.

To investigate the effects of lomerizine, a Ca2+ antagonist, on the ocular tissue circulation in rabbits and on the circulation in the optic nerve head (ONH) and choroid in healthy volunteers. Lomerizine (0.1 [n=10] or 0.3 [n=11] mg/kg) or vehicle solution (n=11) was injected intravenously in urethane-anesthetized rabbits, and blood flow in the retina, choroid, and iris-ciliary body was measured by the microsphere method and that in the ONH by the H2 gas-clearance method (0.1 [n=6] or 0.3 [n=9] mg/kg or vehicle, n=6). Oral 5 mg lomerizine or placebo was administered to volunteers (n=8) in a crossover study, and in areas of the fovea and ONH, the normalized blur (NB), a quantitative index of blood velocity, was measured, together with blood pressure, heart rate, and intraocular pressure (IOP), before and 1.5, 3, 6, and 9 hours after administration. Blood flow in the rabbit retina increased significantly in the lomerizine-treated group, but blood flow changed little in the choroid or iris-ciliary body. Blood flow in the rabbit ONH also showed a significant increase in the lomerizine-treated group. In human studies, the NB obtained from the ONH during the experimental period showed a small but significant increase in the lomerizine-treated group compared with the placebo-treated group, but no significant intergroup difference was detected in the NB obtained from the fovea or in blood pressure, heart rate, or IOP. Lomerizine increases blood velocity, and probably blood flow, in the ONH and retina in rabbits, and it also increases blood velocity in the ONH in healthy humans, without significantly altering blood pressure or heart rate.