Inhibition of the Antigen Provoked Nasal Reaction by Second-generation Antihistamines in Patients with Japanese Cedar Pollinosis

Background: Epinastine hydrochloride and fexofenadine hydrochloride, the second-generation antihistamines, are largely used in the indication of allergic rhinitis in Japan. The purpose of this study was to compare the protective efficacy of epinastine hydrochloride or fexofenadine hydrochloride using a nasal provocation test with Japanese cedar pollen allergen. Methods: A single-dose, placebo-controlled, single-blind crossover clinical study was conducted in patients with Japanese cedar pollinosis. The pollen exposure was done by the antigen provocation by disc method and involved repeated provocation five times per day. Results: Among the active agents studied—epinastine hydrochloride and fexofenadine hydrochloride—epinastine hydrochloride significantly decreased the number of sneezing attacks and the quantity of nasal discharge for 3 hours after drug administration compared with placebo, a finding supported by the quantity of nasal discharge in the nasal findings. In this study, fexofenadine hydrochloride showed no significant difference compared with placebo. Conclusions: This study demonstrates better protection with epinastine hydrochloride than with fexofenadine hydrochloride or placebo in a nasal provocation test with Japanese cedar pollen allergen