A patient with moderate asthma poorly controlled on low-dose inhaled corticosteroid is considered for add-on therapy. The physician avoids zileuton after reviewing the patient's liver profile and medication list. Zileuton differs from other leukotriene pathway drugs because it:

• A Blocks the cysteinyl leukotriene receptor type 1 and requires dose adjustment in renal failure
• B Antagonizes thromboxane receptors and prolongs bleeding time
• C Inhibits phosphodiesterase 4 selectively and causes weight loss
• D Inhibits 5-lipoxygenase directly, preventing leukotriene synthesis, and carries a risk of hepatotoxicity ✓

Explanation

Zileuton directly inhibits 5-lipoxygenase, blocking formation of all leukotrienes including LTB4, unlike montelukast and zafirlukast which antagonize the CysLT1 receptor. It undergoes hepatic metabolism, is hepatotoxic, and requires monitoring of transaminases. Montelukast, the most tempting distractor, acts at the receptor level and has no meaningful hepatotoxic signal, which is why it dominates clinical practice.

Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.

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Written and medically reviewed by the StethoPrep medical team.