Development of an HPLC method for determining the alpha(2)-adrenergic receptor agonist brimonidine in blood serum and aqueous humor of the eye

A procedure for determining brimonidine [5-bromo-6-(2-imidazolidinylideneam ino) quinoxaline] in biological samples using a reversed-phase isocratic HP LC method is described. The application in blood serum and eye aqueous humo r of patients treated with the Alphagan(TM) ophthalmic solution was carried out by enrichment of samples in brimonidine with solid-phase liquid extrac tion. Brimonidine reached maximum levels in aqueous humor and serum within 2-2.5 h, whereafter a declining pattern was obtained. An approximate 50% le vel of brimonidine was identified in serum at 12 h after ocular administrat ion, whereas in aqueous humor this percentage was determined after a period of 4-5 h. Copyright (C) 1999 John Wiley & Sons, Ltd.