Efficacy and duration of action of the antileukotriene zafirlukast on cold air-induced bronchoconstriction.

The objectives of the study were to assess the magnitude of the effect of the leukotriene receptor antagonist, zafirlukast, against cold air-induced bronchoconstriction following the first dose and to assess magnitude and duration after 5 days of dosing. Nineteen patients with asthma were included. In a randomized cross-over design, either zafirlukast 20 mg or 80 mg b.d. or placebo were given over 5 days. Challenges were performed 3 h post first dose and 3, 8, 12 and 24 h post last dose. The authors assessed the provocative ventilation rate necessary to achieve a 10% (PV10) and 20% (PV20) fall in forced expiratory volume in one second. The median PV20 3 h post first dose was 69.1 L x min-1 for zafirlukast 80 mg compared to 40 L x min-1 for placebo (p=0.004). The corresponding median value for zafirlukast 20 mg was 59.9 L x min-1 (p=0.06). At steady state the differences in PV20, between zafirlukast 80 mg and placebo were significant at 8 h and 12 h post last dose. The corresponding difference for zafirlukast 20 mg was statistically significant at 8 h post last dose. The analysis of PV10 yielded compatible results. There was no significant protection 24 h after last dose. This study has demonstrated that zafirlukast offers significant protection against cold air-induced bronchoconstriction in asthma. The degree and duration of protection were dose-dependent. However, there was a large interindividual variability for the protective effect of this leukotriene receptor antagonist.