LTRA inhibition of exercise-induced bronchoconstriction.

Exercise-induced bronchoconstriction (EIB) affects between 70% and 80% of asthmatic patients. Shortly after strenuous exercise, several inflammatory mediators, including the cysteinyl leukotrienes, induce bronchoconstriction. Evidence of this phenomenon includes the increase in urinary leukotriene E4 excretion after exercise and the inhibition of EIB by the leukotriene synthesis inhibitor zileuton. Similarly, the leukotriene receptor antagonists (LTRAs) montelukast and zafirlukast have significantly reduced the decrease in pulmonary function after exercise and shortened the time to recovery. Because exercise is generally a less predictable event in children, EIB can be more difficult to manage in pediatric than in adult asthmatic patients. However, LTRA use may temper this problem. Montelukast administered once daily at bedtime protected pediatric patients against EIB throughout the entire day. Zafirlukast attenuated EIB within 4 hours of dosing in 6- to 17-year-old patients who had mild to moderate asthma. Currently, inhaled ss2-agonists are widely prescribed for EIB, but when used long term, their efficacy may wane because of tolerance. In contrast, one of the advantages offered by LTRA therapy is the absence of tolerance.