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

ABSTRACT

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.