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Paracetamol ALF — RACP Adult Medicine MCQ

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EasyGastroenterologyParacetamol ALFRACP Adult Medicine

A 25-year-old woman presents with acute liver failure (encephalopathy, INR 4.5, ALT 8500 U/L). She took 30 g of paracetamol 48 hours ago in a deliberate self-harm attempt. She did not present to hospital at the time. Paracetamol level is now undetectable. What is the most likely aetiology?

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Correct answer: A — Paracetamol overdose

Undetectable paracetamol level at 48 hours post-ingestion does NOT exclude paracetamol as the cause — the drug is metabolised but hepatotoxic NAPQI metabolites have already caused damage. Very high ALT (>3000) with rapid rise, history of overdose, and timing are diagnostic. NAC should be continued even with undetectable paracetamol levels in established liver failure. King's College Criteria guide transplant listing.

Reference: eTG – 2024 – Paracetamol Overdose; Austin Health Toxicology