Cholinergic blockade in the prevention of exercise-induced asthma.

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Abstract
The contribution of vagal mechanisms to exercise-induced asthma was studied in 10 adult asthmatic patients using the anticholinergic drug ipratropium bromide. Exercise tests were performed for 8 min on a cycle ergometer, and each individual''s tests were standardized by matching O2 uptake. Two tests were done on each of 3 study days, the 1st being without previous medication and the 2nd preceded by inhalation of ipratropium bromide, 0.1 or 1 mg or saline placebo given 90 min. beforehand. The mean falls in FEV1 [1s forced expiratory volume] and PEFR [peak expiratory flow rate] after the initial tests were very similar on the 3 study days. The mean falls in FEV1 after the 2nd test were 22.3, 19.5 and 12.5% with placebo, 0.1 mg and 1 mg ipratropium bromide, respectively. Only the higher dose was significantly better than placebo. The results were analyzed using a protection index to compare the 1st and 2nd tests each day and 1 mg ipratropium bromide was significantly better than both 0.1 mg and placebo. Similar results were obtained using PEFR. Equal bronchodilatation was produced by the 2 doses of drug. Conventional doses of anticholinergic drugs are not effective in preventing exercise-induced asthma, while large doses may do so in the same group of subjects.