Effects of zafirlukast upon clinical, physiologic, and inflammatory responses to natural cat allergen exposure.

BACKGROUND Leukotriene receptor antagonists have been shown to attenuate physiologic changes in the upper and lower airways induced by allergen challenge. However, it is unknown whether these drugs modulate airway inflammation after exposure to allergen in a natural setting. OBJECTIVE To determine the effects of the oral leukotriene receptor antagonist zafirlukast upon symptoms, changes in pulmonary function, and indices of inflammation in the upper and lower airways induced by natural exposure to cats. METHODS Zafirlukast, 20 mg twice daily, or placebo was administered to 18 cat-allergic asthmatic patients in this randomized, double-blind, crossover study. Cat room challenges were performed after a 1-week period of each treatment. Upper and lower airway symptoms were measured and spirometry performed before and at regular intervals during each challenge. Nasal lavage and sputum induction were performed 24 hours before and after each challenge. RESULTS Zafirlukast significantly improved the prechallenge baseline FEV1 (P = 0.001) and attenuated the decrease in FEV1 induced by cat challenge (P = 0.019). Zafirlukast also significantly reduced lower airway symptoms associated with cat challenge (P = 0.005) but had no effects on nasal symptoms. Although zafirlukast did not significantly differ from placebo in its effects on sputum inflammatory cells or eosinophil cationic protein, it significantly reduced the absolute counts of total white cells, lymphocytes, neutrophils, and basophils in nasal lavage fluid. CONCLUSIONS Zafirlukast, 20 mg twice daily for 1 week, demonstrated a significant protective effect on symptoms of asthma and alterations in pulmonary function induced by natural cat exposure, whereas nasal symptoms and markers of sputum inflammation were not affected by the medication.