Effect of a single dose of inhaled salmeterol on baseline airway caliber and methacholine-induced airway obstruction in asthmatic children

Background: Salmeterol is a new inhaled selelctive β2-adrenergic receptor agonist with a long duration of action. We studied the duration of the bronchodilation and the protective effect against methacholine-induced airway obstruction of a single dose of salmeterol in a double-blind, randomized, placebo-controlled, crossover design. Methods: Seventeen boys and three girls with mild-to-moderate asthma participated in the study. On two separate days either 50 μg salmeterol or placebo was inhaled. FEV1 and PD20 methacholine were determined before and 1, 4, 8, 12, and 24 hours after inhalation. Results: Salmeterol resulted in a significant bronchodilation compared with placebo, up to 12 hours (p = 0.0001). At 24 hours there was a residual effect that approached significance; mean FEV1 being 8.3% ± 2.4% above baseline (p = 0.06). Significant protection against airway sensitivity to methacholine after salmeterol inhalation was found at all time points (p < 0.005). Twenty-four hours after administration mean PD20 was still 1.22 ± 0.29 doubling dose above baseline. No important adverse effects were noted. Conclusion: We conclude that a single dose of 50 μg salmeterol in children with asthma gives a long-lasting bronchodilation, exceeding 12 hours, which is comparable to the results in adult studies. The duration of the protection against airway sensitivity to methacholine exceeds 24 hours.

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