A 55-year-old man on sertraline 100 mg daily is admitted with community-acquired pneumonia and started on oral linezolid. On day 3 he develops tremor, clonus at the ankles, hyperreflexia, diaphoresis, and a temperature of 38.6 degrees Celsius. Which property of linezolid explains this presentation?
- A It causes central dopaminergic excess
- B It induces hepatic CYP3A4 metabolism of sertraline
- C It inhibits monoamine oxidase ✓
- D It antagonises GABA receptors
Correct answer: C. It inhibits monoamine oxidase
Explanation
Linezolid is a weak non-selective monoamine oxidase inhibitor, so co-prescription with SSRIs such as sertraline can precipitate serotonin syndrome, typically with neuromuscular findings like clonus and hyperreflexia. The combination should be avoided or sertraline withheld during linezolid therapy. Linezolid neither induces CYP3C4 nor acts on dopamine or GABA systems, which eliminates the remaining options.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
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