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


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo, Japan. tamaki-tky@umin.ac.jp
Yasuhiro
Y
Tamaki
Makoto
M
Araie
Yasuhiro
Y
Fukaya
Miyuki
M
Nagahara
Asuka
A
Imamura
Maiko
M
Honda
Ryo
R
Obata
Ken
K
Tomita
D000284:Administration, Oral; D000328:Adult; D000818:Animals; D001775:Blood Circulation / Q000187:drug effects; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002121:Calcium Channel Blockers / Q000008:administration & dosage / Q000494:pharmacology*; D002829:Choroid / Q000098:blood supply; D002924:Ciliary Body / Q000098:blood supply; D018592:Cross-Over Studies; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007275:Injections, Intravenous; D007429:Intraocular Pressure / Q000187:drug effects; D007498:Iris / Q000098:blood supply; D017078:Laser-Doppler Flowmetry; D008863:Microspheres; D009898:Optic Disk / Q000098:blood supply*; D010879:Piperazines / Q000008:administration & dosage / Q000494:pharmacology*; D011817:Rabbits; D012039:Regional Blood Flow; D012171:Retinal Vessels / Q000502:physiology*
D002121:Calcium Channel Blockers; D010879:Piperazines; C052424:lomerizine