Abstract
Background: Olopatadine hydrochloride is an anti-allergic agent with histamine H1 receptor antagonistic action. We investigated the effects of olopatadine on passive anaphylaxis reaction- and compound 48/80-induced conjunctivitis in rats.
Methods: Allergic conjunctivitis was induced in rats passively sensitized by injection of rat anti-ovalbumin (anti-OVA) serum into the upper subconjunctiva of the right eye, followed by intravenous administration of the antigen and Evans blue dye. After 30 min, the amount of dye leaking into the conjunctiva was measured. Non-allergic conjunctivitis was induced in rats by injection of compound 48/80. Olopatadine or other reference compounds were orally given 1 h before the challenge.
Results: The amount of dye leaking into the conjunctiva following passive anaphylaxis was significantly inhibited by oral administration of 0.01-1 mg/kg olopatadine and the ID50 value was 0.093 mg/kg. In the control group, pathological examination revealed edema and lymphocyte infiltration in the conjunctiva and the palpebral skin. Olopatadine, at 0.03 and 0.3 mg/kg, reduced the grade of these pathological findings. The other antiallergic drugs (1 mg/kg loratadine, 0.3 mg/kg epinastine, 0.3 mg/kg cetiridine, 1 mg/kg ebastine, 30 mg/kg fexofenadine and 3 mg/kg chlorpheniramine), when administered orally, inhibited the passive anaphylaxis reaction-induced vascular hyperpermeability of the conjunctiva, as was the case with olopatadine hydrochloride. Subconjunctival administration of compound 48/80 induced vascular hyperpermeability, which is presumably mediated by histamine release. Oral administration of 0.1 and 1 mg/kg olopatadine significantly inhibited the amount of dye leakage.
Conclusion: Orally administered olopatadine is expected to improve allergic conjunctivitis.
