A review of montelukast in the treatment of asthma and allergic rhinitis.

Montelukast sodium (Singulair, Merck) is a selective and orally-active leukotriene-receptor antagonist (LTRA) that inhibits the cysteinyl leukotriene 1 (CysLT1) receptor. Montelukast is an effective and well-tolerated preventative treatment for asthma and allergic rhinitis in adults and children. The upper and lower airway show similar inflammatory responses to allergen challenge. Leukotrienes are inflammatory mediators that are known as the slow-reacting substance of anaphylaxis produced by a number of cell types including mast cells, eosinophils, basophils, macrophages and monocytes. Synthesis of these mediators results from the cleavage of arachidonic acid in cell membranes and they exert their biological effects by binding and activating specific receptors. This occurs in a series of events that lead to contraction of the human airway smooth muscle, chemotaxis and increased vascular permeability. These effects have led to their important role in the diseases of asthma and allergic rhinitis. As these agents lead to the production of symptoms in patients that are asthmatic or allergic, the use of LTRAs, particularly montelukast, may seem appropriate. Clinical trials have shown that montelukast is effective and safe in the treatment of patients with asthma, allergic rhinitis or both diseases.