Leukotriene activity modulation in asthma.

Leukotrienes constitute a class of inflammatory mediators synthesised from arachidonic acid, a product of cell membrane metabolism. Synthesis occurs in the 5-lipoxygenase enzyme pathway, which produces several species of leukotrienes, each with characteristic biological activities. With regard to asthma, the leukotrienes are particularly important because of their ability to directly and potently mediate bronchoconstriction; in addition, they specifically stimulate the secretion of mucus into the airways and the extravasation of fluids and proteins into the airway tissues, both of which contribute to airway obstruction. A number of antileukotriene agents have been developed with the goal of modulating the inflammatory process in various disease states. These agents fall into 2 general classes: leukotriene receptor antagonists and leukotriene synthesis inhibitors. Results of antileukotriene agents in preclinical and clinical trials indicate that antileukotriene agents attenuate the response to challenges with inhaled leukotrienes, cold air, exercise, aspirin and allergen; in addition, they have shown efficacy in clinical asthma and have not been associated with serious adverse effects. Although results to date indicate that these medications are well tolerated and effective in the treatment of asthma, the recent approval by the FDA of 2 antileukotriene agents will give physicians further insight into how patients with asthma respond to them.