[Effect of topical 8-hydroxy carteolol on intraocular pressure and melanin granules].
It was reported that 8-Hydroxycarteolol (8-OH CA), the major metabolite of carteolol hydroxychloride (CA), has a slightly different pharmacological effect from CA. We studied the reduction of intraocular pressure (IOP) on a single eyedrop application of 8-OH CA in albino and pigmented rabbit eyes. To determine the characteristic of 8-OH CA and CA, we investigated the binding ability of these drugs to synthetic melanin. In the present study, topically applied 2% CA did not significantly decrease IOP in albino and pigmented rabbit eyes. Topically applied 0.01, 0.05, 0.1 and 1.0% 8-OH CA significantly decreased the IOP of albino rabbit as did 0.1 and 1.0% 8-OH to pigmented rabbit eyes. The maximum reduction of IOP was 3.5 +/- 0.33 mmHg (mean +/- SEM) in albino rabbit and 3.0 +/- 0.45 mmHg (mean +/- SEM) in pigmented rabbit. Maximum IOP reduction was obtained after 30 min. from topical application in albino rabbit, but in pigmented rabbit after 1 hour or later. Our binding studies to melanin show that the melanin binding ability is less for 8-OH CA than for CA at any concentrations. These results may indicate that lower concentrations of topically applied 8-OH CA profoundly reduce IOP compared to CA, and 8-OH CA has less effect on melanin than CA.
Hirota
A
A
Department of Ophthalmology, Hiroshima University School of Medicine, Japan.
Mishima
H
H
Kiuchi
Y
Y
Nagata
A
A
Kurokawa
T
T
Ishibashi
S
S
D000287:Administration, Topical; D000818:Animals; D002354:Carteolol / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D008543:Melanins / Q000378:metabolism*; D009883:Ophthalmic Solutions; D011817:Rabbits
D008543:Melanins; D009883:Ophthalmic Solutions; C060345:8-hydroxycarteolol; D002354:Carteolol