Serotonin Syndrome — RACP Adult Medicine MCQ

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ModerateClinical PharmacologySerotonin SyndromeRACP Adult Medicine

A 60-year-old man with chronic pain is on pregabalin 300 mg BD, oxycodone CR 40 mg BD, and duloxetine 60 mg daily. He presents with myoclonus, agitation, hyperthermia, clonus, and hyperreflexia. What is the diagnosis?

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Correct answer: E — Serotonin syndrome

The combination of agitation, hyperthermia, myoclonus, clonus, hyperreflexia, and diaphoresis in a patient on serotonergic medications is serotonin syndrome. Both duloxetine (SNRI – serotonergic) and some opioids (tramadol, fentanyl, oxycodone to a lesser extent) have serotonergic activity. While oxycodone has weak serotonergic effects, the combination with duloxetine can occasionally trigger serotonin syndrome. Treatment includes cessation of all serotonergic agents, supportive care (cooling, benzodiazepines for agitation/myoclonus), and cyproheptadine (5-HT2A antagonist) for moderate-severe cases.

Reference: AMH – 2025 – Serotonin Syndrome; eTG – 2025 – Toxicology