A drug that prevents or alleviates bronchoconstriction in asthma by blocking the production or action of naturally occurring leukotrienes; may also be useful in psoriasis.In 1940 a naturally occurring mediator of asthmatic bronchoconstriction, distinct from histamine and with a longer duration of action, was isolated and named slow-reacting substance of anaphylaxis (SRS-A). Analysis has shown this agent to consist of three cysteinyl leukotrienes, called C4, D4, and E4. The last-named substance, of which the others are precursors, is the most potent. Leukotrienes are eicosanoids derived from arachidonic acid, which is present in cell membranes. The cysteinyl leukotrienes, which are elaborated by bronchopulmonary mast cells, eosinophils, and probably alveolar macrophages, have been shown to mediate bronchoconstriction induced by exercise, hyperventilation in cold air, aspirin, and inhaled allergens; they act by stimulating a specific receptor, known as cysteinyl leukotriene receptor type 1 (CysLT1). Antileukotrienes with clinical usefulness in asthma include zileuton, which inhibits 5-lipoxygenase, an enzyme critical in the biosynthesis of leukotrienes, and leukotriene receptor antagonists (cinalukast, montelukast, zafirlukast, and others). Antileukotrienes reverse bronchoconstriction in asthma to a lesser degree than β2-adrenergic agonists, but their effects are additive to those of the latter agents. In chronic asthma, antileukotrienes improve peak flow and FEV1 and reduce the frequency and severity of acute asthmatic attacks, the need for β2-agonists, and the need for corticosteroid rescue. They are particularly effective in the prophylaxis of exercise- and aspirin-induced asthma; in contrast, many persons with allergic asthma show little or no response. Antileukotrienes are not indicated in the treatment of an acute asthmatic attack or in mild, intermittent asthma controlled adequately with occasional use of inhaled β2-agonists. They have not been recommended as a substitute for inhaled corticosteroid in prophylaxis of asthma. An antagonist of the leukotriene LTB4 receptor in skin cells has shown promise in the treatment of psoriasis. Antileukotrienes are administered orally or by inhalation. Both onset and waning of clinical effects are gradual. Side effects are minimal, but drug interactions may occur because of interference with cytochrome P-450 enzymes. Rare transitory elevations of hepatic aminotransferase have been reported with some agents.

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an·ti·leu·ko·tri·ene (an″te-) (an″ti-loo″ko-triґēn) an agent that interferes with leukotriene synthesis or binding; used in the treatment of asthma.

Medical dictionary. 2011.

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