Time efficacy of a single dose of montelukast on exercise-induced asthma in children.

The aim of this study was to evaluate the timing of onset and the duration of action of a single oral-dose treatment with montelukast in comparison to placebo on exercise-induced asthma (EIA) in asthmatic children. Nineteen children (7-13 years) with stable asthma were evaluated. Patients undertook three consecutive treadmill exercise tests, respectively, 2, 12 and 24 h after a single-dose administration. A double-blind randomized, single-dose, placebo-controlled, crossover design was used. To assess bronchoconstriction after the exercise challenge, the maximal percentage fall in FEV1 (DeltaFEV1) from the baseline value was considered. Two hours after dosing, DeltaFEV1 was -15.33 +/- 2.93 for placebo and -13.33 +/- 2.03 for montelukast. At 12 h, DeltaFEV1 was -18.69 +/- 2.83 for placebo, -9.78 +/- 1.85 for montelukast (p < 0.005). No difference was observed between placebo (DeltaFEV1-10.21 +/- 2.07) and montelukast (DeltaFEV1-9.10 +/- 2.02) at 24 h. Analysis of the degree of protection showed a significant efficacy of montelukast (p = 0.02) in comparison with placebo only at 12 h. Montelukast showed a significant protective effect 12 h after dosing, but no effect after 2 and 24 h. In mild asthmatics, the timing of administration of single dosage before exercise should be strictly considered in order to obtain the drug protective effects.