Effects of Antiglaucoma Drugs on Ocular Blood Flow in Ocular Hypertensive Rabbits

Abstract

Antiglaucoma drugs were studied systematically on the ocular blood flow in ocular hypertensive rabbits. As expected, pilocarpine, clonidine and acetazolamide were all found to increase the ocular blood flow in the retina and choroid.However, their use in the clinics was much less than the /9-blockers, such as Ltimolol, levobunolol, betaxolol and metipranolol. It was surprising to find that all non-specific and /?]-specific adrenergic blockers decreased the ocular blood flow in ocular hypertensive rabbits. If this finding holds true in human patients, the use of yô-blockers for glaucoma treatment should be reconsidered. Dopamine antagonists, such as droperidol, metoclopramide and loxapine, were found to increase the ocular blood flow. Therefore, they might be able to replace ß-blockers for glaucoma treatment.

Canine Retinal Arterial and Arteriolar Dilatation Induced by Nipradilol, a Possible Glaucoma Therapeutic

“…The potency differ ence in the two drugs may be due to the num bers of nitrate esters per molecule (GTN 3 vs. nipradilol 1) or due to the efficacy of the de nitrification enzyme [17], Nipradilol-induced vasodilatation was seen 15 s after the injec tion; the ocular blood flow is expected to be increased. The blood flow increase may be one of the mechanisms underlying the reduc tion of the intraocular pressure [4], In fact, the relationship between ocular blood (low and decreased ocular pressure is suggested from results obtained in anesthetized rabbits [3],…”

“…In addition to cholinergic agonists and p-and cti-adrenoceptor antagonists, attention is thus directed to NO donors as new therapeutics of glaucoma or ocular hypertension. Mechanisms of ocular hypotensive action include a decrease in aqueous humor formation and an increase in outflow or drainage of the humor and in ocu lar blood flow [4], Nipradilol, recently devel oped as an antianginal [5,6] or systemic hypo tensive agent [7], has an NO? moiety in its chemical structure, induces vasodilatation by activating soluble guanylate cyclase, and in creases the production of cyclic guanosine monophosphate (GMP) [8].…”

Effects of Some Natural Flavonoids on Retinal Function Recovery After Ischemic Insult in the Rat

“…Certain eye diseases such as glaucoma, ischemic retinopathy, and age-related macular degeneration are related to the malfunction of ocular circulation/blood flow (1)(2)(3)(4)(5)(6)(7). Therefore, the search for drugs that can improve ocular blood flow, particularly in retina and choroid, is warranted.…”

Effect of Betaxolol, Timolol and Nimodipine on Human and Pig Retinal Arterioles

“…It has long been debated whether these agents also act directly on the retinal circulation to change retinal blood flow. Although the influence of β-adrenergic antagonists on retinal artery diameter has been studied in animals, in-vivo and in a clinical setting, the results remain controversial with some reports suggesting that some β-and the β " -selective adrenergic antagonists decreased ocular blood flow (Yan and Chiou, 1987 ;Chiou and Chen, 1993), whereas other studies have indicated increased blood flow (Grunwald, 1986). This is an important issue as if an IOP reducing agent also causes a reduction in blood flow to the retina then its overall clinical value would have to be in question, especially as there is much evidence that implicates reduced blood flow as another major factor in some glaucoma pathologies (Flammer, 1996).…”