A study of the clinical efficacy of azelastine in patients with extrinsic asthma, and its effect on airway responsiveness.

1. The effect of 4.4 mg azelastine administered orally on airway responsiveness, skin prick testing, daily peak expiratory flow rates and symptoms of asthma was compared with placebo in a 7 week double-blind, parallel group study of 24 patients with extrinsic asthma. The study was in two parts: a 2 week assessment period, during which all patients received placebo tablets but recorded daily peak flow rates (PEFRs) and symptoms, preceding the 7 week double-blind comparison. 2. Azelastine, 4.4 mg, significantly decreased airway responsiveness to histamine compared with placebo both after a single dose (P less than 0.001), and following 7 weeks continuous treatment (P less than 0.02). Airway responsiveness to methacholine was not altered by administration of azelastine compared with placebo. 3. Skin prick test weal diameters to both allergen and histamine were significantly reduced after both a single dose and following 7 weeks continuous therapy treatment with azelastine. 4. There was a significant improvement in both the mean of the morning and the evening peak flow rates recorded during the last week compared with the first week of the study in the group receiving 4.4 mg of azelastine twice daily compared with placebo. Scores for wheeze were significantly reduced during the final 3 weeks of the study in patients receiving azelastine compared both with those receiving placebo and with the first week of the study (P less than 0.05, P less than 0.01). Consumption of inhaled bronchodilators fell significantly during the study in the group receiving azelastine therapy (P less than 0.05); no such fall occurred in the placebo treated patients. 5. A bitter metallic taste was reported by 58% of patients who received azelastine therapy.