SUPPRESSION OF THE SKIN REACTION TO HISTAMINE BY EBASTINE

Background: Ebastine is a nonsedating histamine H-(1) antagonist under going evaluation for treatment of allergic rhinitis and urticaria. Obj ective: To compare the suppression of prick and intradermal skin react ions to histamine over a period of 24 hours produced by a single dose of ebastine, Also to record side effects and assess changes in the ele ctrocardiogram, particularly the QTc interval. Method: Single doses of 1, 3, 10, and 30 mg of ebastine or placebo were administered double-b lind at approximately 8 AM after baseline measurement of the reaction to intradermal testing with 5 mu g histamine base and prick skin testi ng with three concentrations of histamine. Intradermal testing with hi stamine was repeated hourly for four hours, every two hours for eight hours, and after 24 hours. Titrated prick skin testing with histamine was performed at 6, 12, and 24 hours, Potential side effects were reco rded each time skin testing was performed, Electrocardiograms were rep eated at 4 and 24 hours. Results: Intradermal skin test reactions were suppressed between 4 and 24 hours and prick skin tests to 10 mg/mL hi stamine base were suppressed between 6 and 2 1 hours with all doses of ebastine, Prick skin test reactions were significantly smaller at 12 and 24 hours in the group receiving the 30 mg dose of ebastine than in all other groups, Conclusion: Ebastine is a potent antihistamine that suppresses skin reactions to histamine for 24 hours following single doses in the doses tested (1 to 30 mg), No differences from placebo we re noted in either the incidence of side effects or in the QTc interva ls of serial electrocardiograms.