Which of the following statements about montelukast is CORRECT?
- A It is a cysteinyl leukotriene CysLT1 receptor antagonist, blocking LTD4-mediated bronchoconstriction ✓
- B It inhibits 5-lipoxygenase enzyme, reducing leukotriene synthesis
- C It blocks the release of leukotrienes from mast cells by stabilising mast cell membranes
- D It is a thromboxane A2 receptor antagonist with secondary leukotriene synthesis inhibition
Correct answer: A. It is a cysteinyl leukotriene CysLT1 receptor antagonist, blocking LTD4-mediated bronchoconstriction
Explanation
Montelukast is a selective competitive antagonist at the cysteinyl leukotriene receptor subtype 1 (CysLT1), which mediates bronchoconstriction, mucus secretion, and airway inflammation triggered by LTC4, LTD4, and LTE4. It does not affect leukotriene synthesis (that would be 5-lipoxygenase inhibition, the mechanism of zileuton). Montelukast is effective in aspirin-exacerbated asthma and exercise-induced bronchospasm, as both conditions involve excess leukotriene production.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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