Effect of Sch1000 in allergen-induced asthma

Abstract

Carefully controlled allergen inhalation tests were carried out in twelve subjects to provoke early asthmatic responses with a mean maximum FEV₁ fall of 30·7 ± 5·2% (mean ± s.d.). Four subjects had additional late asthmatic responses with a maximum mean FEV₁ fall of 21·0 ± 5·9%. The tests were repeated at intervals of 7 days in an identical way, following inhalation of Sch1000 (80 μg) and placebo, each given 45 min before the onset of the early asthmatic response. This dose of Sch1000 produced a marked and uniform inhibition of methacholine-induced bronchoconstriction in the same subjects. The allergen-induced responses were reproducible in eleven out of the twelve subjects; the coefficient of variation for the decrease in FEV₁ in the early responses being ±7% and in the late response ±43%. Sch1000 produced a slight and variable inhibition of early asthmatic responses (P<0·02) and no inhibition of late asthmatic responses. We examined the relationship between the degree of inhibition of the early asthmatic response by Sch1000 and: (a) the degree of inhibition produced by Sch1000 on histamine- and methacholine-induced bronchoconstriction; (b) the level of non-specific bronchial reactivity measured by inhaled histamine and methacholine; and (c) the degree of bronchodilatation produced by Sch1000. No relationship was found.