Montelukast is used as add-on therapy in aspirin-exacerbated respiratory disease (AERD). It acts by blocking:

• A Leukotriene synthesis by inhibiting 5-lipoxygenase
• B Cysteinyl leukotriene 1 (CysLT1) receptors on airway smooth muscle and inflammatory cells, preventing LTC4/LTD4/LTE4-mediated bronchoconstriction and eosinophil recruitment ✓
• C Phosphodiesterase-4 in airway smooth muscle, increasing cAMP and causing bronchodilation
• D High-affinity IgE receptor on mast cells, preventing mast cell degranulation

Explanation

Montelukast is a cysteinyl leukotriene receptor 1 (CysLT1) antagonist. In AERD, COX-1 inhibition by aspirin diverts arachidonic acid to the 5-lipoxygenase pathway, dramatically increasing cysteinyl leukotriene production (LTC4, LTD4, LTE4), which cause bronchoconstriction, mucus secretion, and eosinophil recruitment. Blocking CysLT1 receptors attenuates these effects. Zileuton inhibits 5-lipoxygenase. Roflumilast/theophylline inhibit phosphodiesterase. Omalizumab blocks free IgE (anti-IgE) rather than the receptor.

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

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Written and medically reviewed by the StethoPrep medical team.