There were 11 trials evaluating the efficacy of zafirlukast in patients with asthma, including 8 trials where asthma was experimentally induced.
According to the results from 8 trials, zafirlukast antagonised exercise-induced bronchoconstriction, and blockws both early- and late-phase responses following allergen provocation in patients with atopic asthma.
A 6-week, multicentre, double-blind, randomised, dose-ranging study evaluated the efficacy of oral zafirlukast (20, 10 or 5 mg twice daily) versus placebo. Of the three zafirlukast dosages, the 20-mg twice-daily dosage produced consistently significant (p<0.05) improvements relative to placebo, by reducing night-time awakenings, first-morning asthma symptoms, daytime asthma symptom scores and albuterol use, and by increasing peak expiratory flow rates and forced expiratory volume. A 13-week multicentre trial with 762 patients found that zafirlukast (20 mg twice daily) significantly decreased daytime asthma symptom scores, night-time awakenings, mornings with asthma, and beta-agonist use, and improved morning peak expiratory flow rates.
A multicentre trial found that both zafirlukast and cromolyn were significantly more effective than placebo (p<0.05), with the two drug treatments exhibiting comparable efficacy.
The available data indicated that zafirlukast was well tolerated. Greater efficacy was noted following oral administration than with aerosol dosing, presumably because of the enhanced delivery of an ingested drug compared with an inhaled one.