A 5-year-old child with moderate persistent asthma is prescribed a leukotriene receptor antagonist (LTRA). Montelukast blocks which receptor to prevent bronchoconstriction and airway inflammation?

• A BLT1 receptor (leukotriene B4 receptor), blocking neutrophil chemotaxis to the airways
• B 5-lipoxygenase enzyme, preventing all leukotriene synthesis
• C CysLT1 receptor (cysteinyl leukotriene receptor 1), blocking LTC4, LTD4, and LTE4-mediated bronchoconstriction and mucus hypersecretion ✓
• D CysLT2 receptor on airway smooth muscle mediating oedema formation

Explanation

Montelukast is a selective, competitive CysLT1 receptor antagonist. Cysteinyl leukotrienes (LTC4, LTD4, LTE4) activate CysLT1 receptors on airway smooth muscle and mucous glands, causing bronchoconstriction, increased mucus secretion, and airway oedema. Blocking CysLT1 reduces airflow obstruction, decreases exercise-induced bronchospasm, and has anti-inflammatory effects by reducing eosinophil recruitment. Zileuton inhibits 5-lipoxygenase enzyme upstream. BLT1 mediates neutrophil chemotaxis by LTB4; CysLT2 receptors are less relevant clinically and not the target of marketed LTRAs.

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

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Written and medically reviewed by the StethoPrep medical team.