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

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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 (FEV1) 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 FEV1 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 FEV1 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 FEV1 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.

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Supported by grants from the Medical Research Council of Canada and Boehringer Ingelheim Canada, Ltd.

Research Fellow in Pharmacology and Respirology sponsored by Boehringer Ingelheim Canada, Ltd.

∗∗

Fellow of the Medical Research Council of Canada.

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