Montelukast

Montelukast is a leukotriene receptor antagonist used for the prevention and chronic management of asthma and for the relief of allergic rhinitis, with an approved role in preventing exercise-induced bronchoconstriction in some patients. It is available as generic tablets, chewable tablets, and oral granules, and is marketed under brand names including Singulair.

Mechanism of action: Montelukast selectively antagonizes the cysteinyl leukotriene receptor CysLT1, blocking the action of leukotrienes C4, D4, and E4. By inhibiting these mediators, it reduces bronchoconstriction, airway edema, and mucus production, contributing to improved airway function.

Uses: It is indicated for prophylaxis and chronic treatment of asthma, relief of seasonal and perennial allergic rhinitis symptoms, and prevention of exercise-induced bronchoconstriction in appropriate patients. It is generally not used for acute asthma attacks and may be added to inhaled corticosteroids when asthma control is not optimal.

Forms and dosing: Montelukast comes in tablets, chewable tablets, and oral granules. Dosing is age- and weight-based and is typically taken once daily, often in the evening, with specific doses depending on indication and formulation.

Pharmacokinetics: The drug is well absorbed, with an oral bioavailability of about 63%. It is extensively metabolized in the liver by cytochrome P450 enzymes, including 2C8, 3A4, and 2C9, and its metabolites are excreted mainly in feces. The elimination half-life of the parent compound is about 2.7 to 5.5 hours.

Safety: Montelukast is generally well tolerated. Common adverse effects include abdominal pain and headache; rare neuropsychiatric events such as mood changes or agitation have been reported. Patients should monitor for behavioral changes and seek medical care if concerned. It should not be used to treat an acute asthma episode.