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Serotonin toxicity associated with linezolid and sertraline — MRCEM SBA MCQ

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HardMental health and behavioural emergenciesSerotonin toxicity associated with linezolid and sertralineMRCEM SBA

A 40-year-old woman taking sertraline for depression and an unchanged dose of quetiapine for two years is brought to the emergency department because of agitation. Linezolid was started yesterday for a culture-confirmed MRSA wound infection. She has since developed diarrhoea and profuse sweating. Her temperature is 39.1°C, pulse 132/min and blood pressure 166/92 mmHg. She is alert but restless, with brisk lower-limb reflexes and inducible ankle clonus. Her airway and breathing are stable. Which initial management and disposition plan is most appropriate?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Withhold sertraline and linezolid; give intravenous benzodiazepine, intravenous fluids and active cooling; arrange acute medical admission.

The rapid onset after linezolid was added to sertraline, together with diarrhoea, diaphoresis, hyperreflexia and inducible clonus, indicates serotonin toxicity. Linezolid can interact with SSRIs to cause potentially life-threatening serotonin syndrome. Both implicated medicines should be withheld while an alternative antibiotic is arranged. Her agitation and temperature of 39.1°C call for benzodiazepine sedation, fluids and prompt active cooling. Moderate-to-severe toxicity requires management in an acute medical facility, with reassessment for deterioration. ([medicines.org.uk](https://www.medicines.org.uk/emc/product/7300/smpc?utm_source=openai)) B includes a possible adjunct, cyproheptadine, but omits immediate cooling and benzodiazepine treatment of this agitated, hyperthermic patient. C is tempting because quetiapine raises the possibility of neuroleptic malignant syndrome; the abrupt onset, diarrhoea and clonus instead favour serotonin toxicity, and C leaves sertraline in place. D gives appropriate initial treatment but places an actively hyperthermic patient in a psychiatric rather than acute medical setting. E substitutes paracetamol for treatment of agitation and neuromuscular activity; active cooling alone does not correct that omission. The wound infection still needs an alternative antimicrobial plan. ([rightdecisions.scot.nhs.uk](https://www.rightdecisions.scot.nhs.uk/mypsych-app/working-in-greater-glasgow-clyde/medicines-companion/emergencies-2222/neuroleptic-malignant-syndrome-nms/?utm_source=openai))

Reference: Linezolid 2 mg/ml Solution for Infusion — Summary of Product Characteristics, sections 4.4–4.5 (Current product information checked September 2026) — https://www.medicines.org.uk/emc/product/7300/smpc NHS Greater Glasgow and Clyde — Serotonin syndrome (Reviewed 1 April 2025) — https://www.rightdecisions.scot.nhs.uk/mypsych-app/working-in-greater-glasgow-clyde/medicines-companion/emergencies-2222/serotonin-syndrome/ NHS Greater Glasgow and Clyde — Neuroleptic malignant syndrome (2025) — https://www.rightdecisions.scot.nhs.uk/mypsych-app/working-in-greater-glasgow-clyde/medicines-companion/emergencies-2222/neuroleptic-malignant-syndrome-nms/