Ocular hypotensive effect of 8-hydroxycarteolol, a metabolite of carteolol

8-hydroxycarteolol hydrochloride (8-OH carteolol) is a main metabolite of carteolol hydrochloride (carteolol). We conducted a randomized double-masked single-drop study in an attempt to compare the effects of the ophthalmic solution of 8-OH carteolol and carteolol on intraocular pressure (IOP) in rabbits with water-load and monkeys. Both 8-OH carteolol (0.01 and 0.1%) and carteolol (1 and 2%) suppressed the water-load induced IOP rise in rabbits. 8-OH carteolol was more effective in suppressing the water-load induced IOP rise in rabbits compared with carteolol on equimolar basis. Both 8-OH carteolol (0.1%) and carteolol (2%) caused a statistically significant decrease in IOP in monkeys. 8-OH carteolol was estimated to be more potent than carteolol in lowering IOP on equimolar basis in monkeys.