Comparison of oral and inhaled metaproterenol for prevention of exercise‐induced asthma

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Abstract
The effectiveness of inhaled vs. oral metaproterenol in preventing exercise-induced asthma (EIA) was studied. Inhaled metaproterenol given 10 min before the exercise significantly reduced the degree of EIA in 24 patients, and in 75% of them completely prevented it. The mean percentage decrease in FEV1 [forced expiratory vol in 1s] was 6.5% with the inhaler and 30.1% with placebo. When inhaled 1 h before the exercise, metaproterenol was still better than placebo but its effectiveness was considerably lower. Metaproterenol tablets had a slight protective effect given 1 h before, and none when administered 2 h before exercise. There was no correlation between the protective effect against EIA and the bronchodilating effect obtained before exercise. Metaproterenol administered by metered-dose inhaler is a very effective prophylactic medication against clincially troublesome EIA, while metaproterenol tablets should not be recommended for this purpose.