Inhibition of histamine-induced skin wheal and flare after 5 days of mizolastine.

Mizolastine is a new, nonsedating antihistamine providing satisfactory symptomatic relief in allergic rhinitis and urticaria. The purpose of this study was to use inhibition of wheal and flare formation after 2-mu g intradermal histamine injections as a measure of the antihistamine effect of repeated doses of mizolastine. Eight volunteers were enrolled in this four-arm, double-blind, cross-over, randomized study. Three dose levels of once-daily mizolastine (5 mg, 10 mg, and 15 mg) were compared with placebo during 5-day dose periods. Histamine tests were performed before drug intake on days 1 and 5, and then 2, 3, 4, 6, 8, 10, 12, 14, and 24 hours after drug intake on day 5. All 3 doses of mizolastine were more effective than placebo in suppressing wheal and flare reactions, and the antihistamine activity was highest at both the 10- and 15-mg dose levels. The effect on the flare reaction appeared within 1 hour, reached a maximum effect 4 hours after administration, and persisted for as long as 24 hours. The relative changes in wheal and flare areas were correlated with mizolastine trough plasma levels on day 5. Safety was satisfactory in all groups. This study confirms that mizolastine is a rapid and potent antihistamine; and its long-lasting effectiveness indicates that a once-daily regimen is acceptable for clinical use.