Management of Asthma: The Potential Role of Zafirlukast
Julie C. Adkins
Asthma is a chronic inflammatory disorder of the airways. The worldwide prevalence of asthma has increased in recent decades. There is an approximately 20-fold variation (range 1.6% to 36.8%) in the prevalence of childhood asthma throughout the world. The highest prevalence rates are in the UK, Australia, New Zealand, the Republic of Ireland and Canada. The indirect costs of asthma, which include absence from school, lost productivity and premature death, are substantial. The goals of asthma therapy include controlling the disease and maintaining the well-being of the patient. Identification and avoidance of factors that precipitate asthma attacks are important in achieving satisfactory control of asthma. A stepped-care approach to drug therapy, in which anti-inflammatory therapy is the cornerstone, is recommended. Zafirlukast is a cysteinyl leukotriene type 1 receptor antagonist that causes bronchodilation and has anti-inflammatory properties. Oral zafirlukast 20mg twice daily was more effective than placebo in relieving symptoms, improving lung function, reducing requirements for as-needed beta2-agonists and preventing exacerbations in patients >=12 years of age with mild to moderate asthma. Zafirlukast 20mg twice daily produced improvements in symptoms and reductions in as-needed beta2-agonist rescue medication similar to inhaled sodium cromoglycate in patients with asthma. As an alternative to inhaled corticosteroids, zafirlukast 20mg twice daily produced improvements in night-time wakenings, mornings with asthma and reductions in the use of beta2-agonist rescue medication in patients with mild to moderate asthma. However, beclomethasone dipropionate 200 to 250microg twice daily produced greater improvement than zafirlukast in all efficacy parameters and significantly greater improvements in morning peak expiratory flow rate, forced expiratory volume in 1 second and daytime symptoms than zafirlukast. In patients with asthma uncontrolled on low dosages of inhaled corticosteroids, the addition of oral zafirlukast 40 or 80mg twice daily was as effective as doubling the dose of the inhaled corticosteroid. The most common adverse events associated with zafirlukast in trials <=20 weeks long were pharyngitis, headache and aggravation reactions, the incidence of which was similar to that in placebo recipients. Drug-drug interactions involving zafirlukast and aspirin, erythromycin, terfenadine, theophylline and warfarin have been described. Zafirlukast is indicated for the prophylactic treatment of chronic asthma. The drug is currently recognised in the US guidelines as an alternative to inhaled corticosteroids in patients aged >=12 years with mild persistent asthma. As an adjunct to corticosteroids, the role of zafirlukast is still evolving, but it seems likely that patients with asthma of all severities may benefit from the drug.
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