ONSET OF ACTION, EFFICACY, AND SAFETY OF A SINGLE-DOSE OF FEXOFENADINE HYDROCHLORIDE FOR RAGWEED ALLERGY USING AN ENVIRONMENTAL EXPOSURE UNIT

Background: Fexofenadine hydrochloride is the active acid metabolite o f terfenadine. Fexofenadine's anti-allergic properties require confirm ation in a clinical setting. Objective: The purpose of this study was to characterize the time to onset of clinically important relief of sy mptoms of allergic rhinitis in subjects taking single doses of either 60 mg or 120 mg fexofenadine HCl, or placebo, after exposure to ragwee d pollen in a controlled environment. Other objectives were to assess the efficacy and safety of single doses of fexofenadine HCl. Methods: One hundred forty-six ragweed-sensitive subjects were primed in the of f-season with ragweed pollen in the environmental exposure unit. One h undred thirty-six subjects who adequately responded to priming entered a single-dose placebo phase. Placebo-responders were disqualified fro m the study, leaving 99 subjects with adequate symptoms to be randomiz ed and given a single dose of either fexofenadine HCl 120 mg (33), 60 mg (33) or placebo (33), after 60 minutes of allergen exposure. Exposu re continued over five hours and subjects recorded symptoms every 20 m inutes. This study was of a randomized, placebo-controlled, double-bli nd, parallel design. Results: Median time to onset for relaxed criteri a clinically important relief was 60 minutes for both fexofenadine tre atment groups, and 100 minutes for placebo (P = .018). The proportion with relief was 82% at 60 mg, 85% at 120 mg, and 64% for placebo. Trea ted groups had reductions in symptom scores double that of placebo. Co nclusions: Fexofenadine is safe and efficacious at single doses of 60 mg and 120 mg. Average time to onset was 60 minutes using controlled p ollen exposure in an environmental exposure unit.