Comparative study of commercially available antihistaminic drops in an animal model of early phase allergic conjunctivitis

Purpose: To compare the relative efficacy of topical ocular antihistaminic drops with balanced saline solution (BSS) and benzalkonium chloride (BC) in the early phase of allergic conjunctivitis in animal model. Methods: 80 male guinea pigs were sensitized with intraperitoneal egg albumin (EA) and alum. Eighteen days after sensitization the animals were topically challenged by conjunctival instillation of EA. The animals were treated 15 minutes before and 15 minutes after challenge with commercially available drugs. Ketotifen with and without preservative, olopatadine, azelastine, spaglumic acid and emedastine were tested. BSS and BC drops were tested as controls. Different drops were tested in the right and the left eye of each animal to avoid interanimal differences in allergic reactivity. The allergic reaction was measured by intravenous Evans blue extravasation (EBE) under general anaesthesia. Results: Two animals could not be used for evaluation. EBE was highest in the eyes treated by azelastine, olopatadine and preservative free ketotifen, and lowest in the eyes treated by spaglumic acid. However, when the results of the right and left eyes of each animal were considered EBE was higher in the eyes treated by BSS and BC and lowest in the eyes treated by spaglumic acid and emedastine. Conclusions: Spaglumic acid and emedastine seem to be the most useful drugs to reduce EBE in an animal model of early phase allergic conjunctivitis.