A randomized, double-blind, placebo-controlled trial of the effect of zafirlukast on upper and lower respiratory responses to cat challenge

Background: Zafirlukast, a leukotriene antagonist, has been shown to have protective effects against a variety of asthma triggers. Objective: Our purpose was to evaluate zafirlukast's effects on upper and lower airway responses to cat allergen exposure with use of a well-characterized cat exposure model. Methods: In a double-blind, placebo-controlled, cross-over trial 18 subjects with cat-induced asthma were randomly assigned to receive 1 week each of zafirlukast or placebo followed by a 1-hour cat challenge. Upper and lower respiratory symptoms were rated and spirometry and acoustic rhinometry were performed. Challenges were stopped early if the subject was too uncomfortable or had a >50% decrease in FEV₁. Results: Overall changes in FEV₁ were significantly different with zafirlukast treatment (P = .02). Significant differences in FEV₁ change were detected at 15 and 30 minutes (P = .027 and .05, respectively) but not at 45 and 60 minutes. Changes in acoustic rhinometry were also significantly different at 15 and 30 minutes (P = .05 and .0005, respectively) but not at 45 and 60 minutes. Challenge length was significantly longer with zafirlukast versus placebo after adjustment for differences in allergen exposure (P = .022). Respiratory symptom scores were significantly different (lower respiratory, P < .001; upper respiratory, P = .038) through the first 30 minutes of the challenge after adjustment for allergen exposure. Conclusions: Zafirlukast was significantly more effective than placebo in preserving pulmonary function and nasal anatomy and extending challenge length when cat-sensitive asthmatic subjects were exposed to high levels of cat allergen.