A comparison of the protective effect of fenoterol and Sch1000 on allergen-induced asthma

Abstract

The protective effects of inhaled Sch1000 (80 μg), inhaled fenoterol (800 μg), and placebo on the early asthmatic response induced by inhaled allergen were compared in 10 subjects in a single-blind investigation. Allergen inhalation produced early asthmatic responses in all 10 subjects, with a mean 1-sec forced expiratory volume (FEV 1) fall of 31.1% (range, 23% to 40%). The similarity of the responses to allergen inhalation following no pretreatment and following placebo showed that the allergen-induced response was highly reproducible, with coefficients of variation for the maximum percentage FEV 1 fall of ± 7.2%. Sch1000 produced a slight nonsignificant reduction in the magnitude of the early asthmatic response of 20.7% ± 39.7% ( p > 0.10) for the maximum FEV 1 fall. Fenoterol, however, produced a highly significant reduction in the magnitude of the early of 76.4% ± 23.5% ( p < 0.001) for the maximum FEV 1 fall, which was significantly greater than that produced by Sch1000 ( p < 0.001). These results show that β-adrenergic agonists, such as fenoterol, are more effective than cholinergic antagonists, such as Sch1000, in preventing the early asthmatic response induced by inhaled allergen. Reflex parasympathetic bronchoconstriction is involved to a variable and minor extent in the production of allergen-induced early asthmatic responses.