OSCE — Tricyclic Antidepressant (TCA) Overdose

Brief (to candidate)

You will assess a patient with a presentation consistent with Tricyclic Antidepressant (TCA) Overdose. You have 8 minutes to take a focused history, outline examination, investigations, and management including red flags. ^[1][4][7]

Clinical context

Tricyclic antidepressant overdose (amitriptyline, imipramine, dothiepin, nortriptyline, clomipramine) is among the most lethal common pharmaceutical poisonings. Sourced teaching for this station: fast sodium-channel blockade (QRS widening, ventricular dysrhythmias, hypotension, seizures, coma), an anticholinergic picture, and circulatory collapse. The ECG — not the serum drug level — predicts seizures and ventricular arrhythmias. Sodium bicarbonate 1-2 mmol/kg (maximum 6 mmol/kg) to serum pH 7.45-7.55 with hyperventilation is the antidote; benzodiazepines for convulsions; norepinephrine after fluids/dopamine fail; lipid emulsion for collapse despite standard therapy. Avoid class Ia/Ic antiarrhythmics, phenytoin, flumazenil, emesis, physostigmine and dialysis. ^[1][4][7]

Candidate tasks

1. Clarify onset, severity, associated features, and red-flag symptoms.
2. State focused examination priorities.
3. List first-line investigations and any named score/criteria.
4. Give immediate resuscitation steps.
5. Outline definitive management with doses/routes where sourced.
6. Name complications and disposition (ward / HDU / theatre / discharge safety-net).
7. Mention one special-population modifier (pregnancy, child, elderly, CKD). ^[1][4][7]

Examiner checklist

^{[1] [4] [5] [7]}

Model outline

Lead with the working diagnosis and life threats. Resuscitate before a drug level. Give sodium bicarbonate for QRS over 100 ms or shock/seizures/ventricular dysrhythmia, targeting pH 7.45-7.55 rather than complete QRS correction. Benzodiazepine for seizures. Norepinephrine for hypotension unresponsive to fluid and dopamine. Lipid emulsion if deterioration continues despite standard therapy including bicarbonate. Document the six-hour observation rule and child-under-6 evaluation after any ingestion. ^[1][4][7]

References12ShowHide

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2. [2]Boehnert MT, Lovejoy FH Jr. Value of the QRS duration versus the serum drug level in predicting seizures and ventricular arrhythmias after an acute overdose of tricyclic antidepressants N Engl J Med, 1985.PMID 4022081
3. [3]Liebelt EL, Francis PD, Woolf AD. ECG lead aVR versus QRS interval in predicting seizures and arrhythmias in acute tricyclic antidepressant toxicity Ann Emerg Med, 1995.PMID 7618783
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5. [5]Glauser J. Tricyclic antidepressant poisoning Cleve Clin J Med, 2000.PMID 11060957
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7. [7]Chan BS, Buckley NA. Common pitfalls in the use of hypertonic sodium bicarbonate for cardiac toxic drug poisonings Clin Toxicol (Phila), 2024.PMID 38597366
8. [8]Hawton K, Bergen H, Simkin S, Cooper J, Waters K, Gunnell D, Kapur N. Toxicity of antidepressants: rates of suicide relative to prescribing and non-fatal overdose Br J Psychiatry, 2010.PMID 20435959
9. [9]Taylor D, Poulou S, Clark I. The cardiovascular safety of tricyclic antidepressants in overdose and in clinical use Ther Adv Psychopharmacol, 2024.PMID 38827015
10. [10]Hendron D, Menagh G, Sandilands EA, Scullion D. Tricyclic antidepressant overdose in a toddler treated with intravenous lipid emulsion Pediatrics, 2011.PMID 22065274
11. [11]Levine M, Brooks DE, Franken A, Graham R. Delayed-onset seizure and cardiac arrest after amitriptyline overdose, treated with intravenous lipid emulsion therapy Pediatrics, 2012.PMID 22753554
12. [12]Teba L, Schiebel F, Dedhia HV, Lazzell VA. Beneficial effect of norepinephrine in the treatment of circulatory shock caused by tricyclic antidepressant overdose Am J Emerg Med, 1988.PMID 3178947