Montelukast, used in aspirin-exacerbated respiratory disease, acts by blocking:

• A 5-lipoxygenase enzyme, preventing leukotriene synthesis
• B Histamine H1 receptors in the bronchial mucosa
• C Prostaglandin E2 receptors in airway epithelium
• D Cysteinyl leukotriene CysLT1 receptors on bronchial smooth muscle and mast cells ✓

Explanation

Montelukast is a selective competitive antagonist at cysteinyl leukotriene CysLT1 receptors. In aspirin-exacerbated respiratory disease (Samter's triad), COX inhibition by aspirin shunts arachidonic acid toward the 5-LOX pathway, increasing cysteinyl leukotrienes (LTC4, LTD4, LTE4) which trigger bronchoconstriction and nasal polyposis. Zileuton (not montelukast) inhibits 5-lipoxygenase directly.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.