Montelukast, used in asthma prophylaxis, blocks which specific mediator pathway?
- A Cysteinyl leukotriene 1 (CysLT1) receptors, preventing bronchoconstriction and eosinophil recruitment by LTC4, LTD4, LTE4 ✓
- B 5-lipoxygenase (5-LOX) enzyme, blocking leukotriene synthesis
- C LTB4 receptor, preventing neutrophil chemotaxis
- D Phosphodiesterase-4 (PDE4), increasing cAMP in airway smooth muscle
Correct answer: A. Cysteinyl leukotriene 1 (CysLT1) receptors, preventing bronchoconstriction and eosinophil recruitment by LTC4, LTD4, LTE4
Explanation
Montelukast and zafirlukast are CysLT1 receptor antagonists; they block the action of cysteinyl leukotrienes (LTC4, LTD4, LTE4) at their receptor on bronchial smooth muscle and eosinophils, reducing bronchoconstriction, mucus secretion, and airway inflammation. Zileuton is the 5-lipoxygenase inhibitor that blocks leukotriene synthesis; roflumilast inhibits PDE4. LTB4 receptor antagonism is not their mechanism.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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