 Zileuton, a specific 5-lipoxygenase inhibitor, has been extensively studied in inflammatory diseases such as asthma, which involve leukotrienes as mediators of inflammation. Zileuton Immediate Release IR tablets Zyflo were approved by the Food and Drug Administration FDA in December 1996 for the prevention and treatment of asthma in adults and children 12 years of age and older. The results of the 2 pivotal studies in asthmatics with zileuton IR tablets demonstrated that zileuton at a dose of 600 mg QID produced and maintained a lasting improvement of lung function. In addition to the lasting effect of zileuton, an acute bronchodilation as early as 60 minutes was observed after administration of the first 600 mg oral dose. 