A 26-year-old woman with aspirin-exacerbated respiratory disease requires add-on therapy. Her physician selects zileuton. The mechanism distinguishing zileuton from montelukast and zafirlukast is:
- A Inhibition of phosphodiesterase type 4 in airway inflammatory cells
- B Antagonism at the CysLT1 receptor
- C Inhibition of 5-lipoxygenase, preventing formation of all leukotrienes including LTB4 ✓
- D Blockade of IgE binding to high-affinity receptors on mast cells
Correct answer: C. Inhibition of 5-lipoxygenase, preventing formation of all leukotrienes including LTB4
Explanation
Zileuton inhibits 5-lipoxygenase, blocking the arachidonic acid pathway upstream so neither cysteinyl leukotrienes (LTC4, LTD4, LTE4) nor LTB4 are formed. Montelukast and zafirlukast are CysLT1 receptor antagonists and leave LTB4 production intact. This makes zileuton uniquely useful in aspirin-exacerbated respiratory disease. Hepatotoxicity requiring liver enzyme monitoring is its characteristic adverse effect.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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