Knowledge Base

Paracetamol Overdose

Knowledge Base

title: "Paracetamol Overdose"

Paracetamol Overdose

Key Facts

Paracetamol toxicity treatment line on Rumack-Matthew nomogram starts at 150 mg/L at 4 hours

Source: Therapeutic Guidelines (eTG) / Poisons Information Centre (Australia).

N-acetylcysteine (NAC) is most effective within 8 hours of paracetamol ingestion

Common Australian hospital protocol for IV acetylcysteine is a 2-bag regimen: 200 mg/kg over 4 hours, then 100 mg/kg over 16 hours (total 300 mg/kg over 20 hours) — follow local toxicology/poisons guidance.

Source: Therapeutic Guidelines (eTG) / Poisons Information Centre (Australia).

Overview

This article covers Nomogram, NAC protocol, High-risk features.

Content for this wiki article will be expanded from the Week 4 material.

Nomogram

  • Use the nomogram for a single acute ingestion with a known time.
  • Take a paracetamol level at ≥4 hours post-ingestion (earlier levels are not interpretable for risk).
  • Treat if the level is on/above the treatment line.
  • If the patient presents >8 hours after ingestion (or time is uncertain), start acetylcysteine while awaiting results and seek toxicology advice.
Warning

The nomogram is not reliable for:

  • Modified-release paracetamol ingestion
  • Staggered/repeated supratherapeutic ingestion
  • Unknown time of ingestion

These scenarios need toxicology/poisons advice and usually repeat levels and/or prolonged acetylcysteine.

NAC protocol

Initial labs (typical):

  • Paracetamol concentration (timed)
  • LFTs, INR (International Normalised Ratio), UEC/creatinine

IV acetylcysteine (common 2-bag regimen):

  1. 200 mg/kg over 4 hours
  2. 100 mg/kg over 16 hours

Reassess at end of infusion:

  • If paracetamol is still detectable and/or ALT is rising, continue acetylcysteine per toxicology advice.

High-risk features

  • Presentation >8 hours post-ingestion
  • Modified-release product ingestion (e.g., sustained-release formulations)
  • Staggered ingestion over many hours
  • Co-ingestion delaying gastric emptying (e.g., opioids/anticholinergics)
  • Evidence of liver injury (rising ALT/AST, rising INR (International Normalised Ratio), hypoglycaemia, encephalopathy)

Sources

  • CC Bible
  • Toxicology Handbook
  • eTG
  • Poisons Information Centre (Australia): 13 11 26

Related Topics

See also: Approach to the Poisoned Patient, Acute Liver Failure