Exercise-induced bronchoconstriction occurs in 80 to 90 percent of children with asthma and can interfere with activities important for social and physical development. Current recommendations for prevention of exercise-induced bronchoconstriction include administration of short-acting beta₂-adrenergic agonists or cromolyn before exercise. Montelukast, a leukotriene receptor antagonist, increases ciliary activity and decreases mucus secretion, venopermeability and eosinophil migration into airways mucosa. Kemp and associates conducted a randomized, double-blind, placebo-controlled crossover study of the effects of montelukast on exercise-induced bronchoconstriction in children with asthma.

The 25 children in the study ranged in age from six to 14 years. They received either montelukast (given in a 5-mg chewable tablet) or placebo once daily in the evening for two days before the exercise challenge. A standardized treadmill exercise challenge was performed approximately 20 to 24 hours after the second dose. Spirometry measurements were obtained 20 and five minutes before the exercise challenge and then at five, 10, 15, 30, 45, 60 and, if necessary, 75 and 90 minutes after exercise.

When compared with placebo, montelukast was associated with a significant reduction in the maximum percentage of fall in the forced expiratory volume in one second (FEV₁). Moreover, the time until recovery was shorter following administration of montelukast, although the difference between montelukast and placebo did not reach statistical significance. Fourteen adverse clinical events were noted (eight in the placebo treatment period and six in the montelukast treatment period). All of them were transient and self-limited.

The authors conclude that montelukast protects against exercise-induced bronchoconstriction throughout the course of a once-daily dosing interval. This therapeutic effect has also been documented in adults during a 12-week treatment period. Montelukast did not, however, provide complete protection against exercise-induced bronchoconstriction in the children studied, as has been reported in previous studies of albuterol and salmeterol. Continuous use of the latter medications has been associated with tolerance. Cromolyn and nedocromil have also demonstrated protection against exercise-induced bronchoconstriction when either agent is administered 15 to 30 minutes before exercise. Beclomethasone has also been shown to provide protection against mild exercise-induced bronchoconstriction in children after one and two months of therapy, but tolerance to the protective effect also developed after three months of therapy.