leukotriene antagonists
Summary
Leukotriene antagonists are oral anti-asthma drugs that block the cysteinyl leukotriene pathway: montelukast and zafirlukast block the CysLT1 receptor, and zileuton inhibits 5-lipoxygenase. They are particularly useful in aspirin-exacerbated respiratory disease (Samter triad) and exercise-induced asthma.
Detail
Cysteinyl leukotrienes (LTC4, LTD4, LTE4) are derived from arachidonic acid via 5-lipoxygenase and cause bronchoconstriction, mucus secretion, and eosinophil recruitment. Drugs: montelukast (once daily, oral, FDA-approved down to age 1) and zafirlukast block the CysLT1 receptor; zileuton inhibits the 5-lipoxygenase enzyme upstream, blocking all leukotriene synthesis. They are second-line agents for persistent asthma and especially useful in aspirin-exacerbated respiratory disease (asthma + nasal polyps + aspirin sensitivity), exercise-induced bronchospasm, and allergic rhinitis. Boards toxicities: montelukast carries a black-box warning for neuropsychiatric effects (mood changes, suicidal ideation); zileuton and zafirlukast can cause hepatotoxicity (monitor LFTs); rare association of Churg-Strauss / eosinophilic granulomatosis with polyangiitis on starting therapy (likely steroid taper unmasking).
Sources
- First Aid for USMLE Step 1 2024
- Sketchy Pharm
- Katzung Basic & Clinical Pharmacology
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