Time-course of aspirin and salicylate in ocular tissues of rabbits

The time courses of aspirin and salicylate in plasma and ocular tissues of rabbits were investigated after the i.v. administration of aspirin. Unhydrolyzed aspirin rapidly disappears from plasma and many ocular compartments but persists up to 4 hours in aqueous and vitreous humours. Salicylate decreases in plasma follow an exponential kinetics; in aqueous humour and in vascularized tissues the behaviour is similar but with a half-life longer than in plasma. In the cornea, lens and vitreous humour, the concentration of salicylate reaches a peak between 2 and 4 hours, then it decreases very slowly. Our results show that aspirin is protected from the hydrolytic action of plasmatic esterases in aqueous and vitreous humours but is rapidly hydrolyzed in the cornea and lens by local esterases present in these tissues. It is possible that both aspirin and salicylate leave the eye by means of an active transport. Our results also indicate that salicylate can accumulate in the cornea, lens and retina when aspirin is administered repeatedly.