Objectives: The long-acting beta2-adrenergic agonist salmeterol prevents exercise-induced asthma, but tolerance may develop to its bronchoprotective effect. We wanted to ascertain if the development of tolerance could be prevented by using a low-dose treatment regimen of 50 microg once daily, instead of the usual dose of 50 microg twice daily, in adolescents receiving regular glucocorticoid inhalations. Methods. In a randomized, double-blind, 2x28-day crossover study, we administered salmeterol (50 microg) or placebo once daily via a metered-dose inhaler and Nebulizer Chronolog device to monitor compliance. Exercise challenge tests were performed 1 and 9 hours after salmeterol or placebo inhalation on the 1st and 28th day of each treatment period. The primary outcome variable was the maximum decrease in percent predicted FEV1 postexercise.
Results: Fourteen subjects with a mean age of 13.1 years completed the study. The first dose of salmeterol had an excellent bronchoprotective effect against exercise-induced asthma at 1 and 9 hours. After the 28th consecutive daily dose of salmeterol, the bronchoprotective effect was significantly greater than that of placebo at 1 hour, but not at 9 hours.
Conclusions: We conclude that a single 50-microg dose of salmeterol has an excellent protective effect against exercise-induced asthma for at least 9 hours, but that this effect may wane during regular once-daily salmeterol treatment, despite the reduced frequency of dosing and despite concomitant use of inhaled glucocorticoids.