Montelukast reduces asthmatic bronchoconstriction by blocking:

• A 5-lipoxygenase, inhibiting leukotriene synthesis from arachidonic acid
• B Cysteinyl leukotriene receptor 1 (CysLT1) on bronchial smooth muscle and mucosal mast cells ✓
• C Phosphodiesterase-4, increasing intracellular cAMP and causing bronchodilation
• D Histamine H1 receptors on bronchial smooth muscle

Explanation

Montelukast is a selective CysLT1 receptor antagonist. Leukotrienes C4, D4 and E4 (cysteinyl leukotrienes) bind CysLT1 receptors on bronchial smooth muscle causing potent bronchoconstriction, increased mucus secretion and mucosal oedema. Montelukast blocks these effects. Zileuton inhibits 5-lipoxygenase (upstream leukotriene synthesis); roflumilast is a PDE-4 inhibitor; antihistamines block H1 receptors and are not useful for asthma.

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

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Written and medically reviewed by the StethoPrep medical team.