The inhibitory effect of azelastine hydrochloride on histamine- and allergen-induced bronchoconstriction in atopic asthma


Prof. S. T. Holgate, Immunopharmacology Group, Medicine 1, Level D, Centre Block, Southampton General Hospital, Tremona Road, Southampton SO9 4XY, U.K.


We have examined the effect of azelastine, a new H1 histamine receptor antagonist, against bronchoconstriction induced by histamine and allergen. Twelve mild, atopic asthmatics each underwent two histamine and two allergen concentration-response inhalation challenges 4 hr after treatment with either 8.8 mg of azelastine or a matched placebo. Following azelastine the dose of histamine required to provoke a 20% fall in FEV1 (PD20 histamine) rose, from a geometric mean of 0.31 mg/ml to < 13.2 mg/ml. Azelastine also significantly inhibited allergen-induced bronchoconstriction, the PD20 allergen rising from 9.3 cumulative breath units (c.b.u.) to < 47.9 c.b.u., a greater than 5-fold increase. We conclude that azelastine effectively inhibits both histamine and allergen-induced bronchoconstriction, with considerably greater potency against histamine.