Login
Search

Search
Search
  1. Home
  2. Category
  3. Gastrointestinal including Liver
  4. Paracetamol Overdose

Paracetamol Overdose

NICE BNF Treatment summaries. Poisoning, emergency treatment. Paracetamol poisoning.

Background Information

Paracetamol overdose can be classified by the timing of ingestion:
 
Type Definition
Acute overdose Ingestion of all the paracetamol tablets within 1 hour
Staggered overdose Ingestion of the paracetamol tablets over more than 1 hour
Therapeutic excess Ingestion of potentially toxic paracetamol dose with the intent to treat pain / fever and without self-harm intent

Guidelines

Antidote of choice for paracetamol overdose is N-acetylcysteine (standard 21-hour regimen, 3 consecutive IV infusion over 1 hour, 4 hour and 16 hour). 
  • Prevents or reduces severity of liver damage if given up to 24 hours of ingestion (possibly beyond 24 hours)
  • Most effective given within 8 hours of ingestion, its effectiveness declines after

Guidelines regarding paracetamol overdose are complicated, therefore the author presented 2 approaches: 1) list of indications to give N-acetylcystine immediately, 2) management depending on the type of overdose. It is recommended to go over both and consolidate the content.
 

The most important and commonly examined indication to give N-acetylcystine is that if serum paracetamol concentration falls on or above the treatment line on paracetamol treatment graph

However, there are separate indications where N-acetylcysteine should be given immediately even without a serum paracetamol concentration:
  • Staggered overdose (all patients)
  • Unclear / unknown timing of ingestion (all patients)
  • Selected patients in acute overdose 
    • <8 hours of ingestion of >150 mg/kg + if there will be a ≥8 hours delay in obtaining paraetamol concentration
    • 8-24 hours after ingestion + >150 mg/kg / unknown dose / symptomatic with jaundice or hepatic tenderness
    • >24 hours after ingestion + >150 mg/kg / unknown dose / jaundice or hepatic tenderness / detectable paracetamol concentration
    • Biochemical tests suggest acute liver injury (e.g. ↑ ALT or INR >1.3)

Give N-acetylcystine immediately (without awaiting for a serum paracetamol concentration)

Give N-acetylcystine immediately (without awaiting for a serum paracetamol concentration)

Consider activated charcoal if patient presents within 1 hour of ingesting paracetamol (>150 mg/kg).

Acute overdose is a bit more complicated with 5 main scenarios:
 
Scenario Management
Ingested <4 hours ago
  • Wait until 4 hours after ingestion, then
  • Measure serum paracetamol concentration, and
  • Only give N-acetylcysteine if paracetamol level is on or above the treatment line
Ingested <8 hours ago + dose >150 mg/kg If there will be a delay of ≥8 hours in obtaining paracetamol levels
  • Give N-acetylcysteine immediately (without waiting paracetamol concentration)
Ingested 8-24 hours ago + any of the following
  • Dose >150 mg/kg
  • Unknown dose
  • Symptomatic with jaundice or hepatic tenderness
  • Give N-acetylcysteine immediately (without waiting paracetamol concentration)
Ingestion >24 hours Give N-acetylcysteine if any of the following:
  • >150 mg/kg
  • Unknown dose
  • Symptomatic (jaundiced or RUQ tenderness)
  • Detectable paracetamol concentration
Biochemical tests suggest acute liver injury (e.g. ↑ ALT, INR >1.3 in the absence of other causes) Give N-acetylcysteine (even if paracetamol concentration is BELOW the treatment line)

If there are any clinical features of hepatic injury (e.g. jaundice / RUQ tenderness) → give N-acetylcysteine immediately
 
Other patients → depend on maximum dose of paracetamol ingested in any 24 hour period (BNF says use TOXBASE, so unlikely examinable)

References

Author: Adams Lau
Reviewer:
Last edited: 07/08/25