Updated paracetamol overdose guidelines

A large percentage of incidents of accidental paediatric and deliberate adult poisoning involve paracetamol. Australasian experts in the field of paracetamol poisoning have updated guidelines for the management of this problem.

The key changes to the previous guidelines, published in 2008, concern indications for administration of activated charcoal; modified-release (MR) and supra-therapeutic ingestions; management of large or massive overdoses; and paediatric liquid ingestion.

Gastric decontamination

  • The revised guideline recommends that 50g of activated charcoal be administered to a co-operative, awake adult within 2 hours of ingestion of a toxic dose of immediate-release (IR) paracetamol and within 4 hours of MR ingestion.
  • In cases of overdoses of >30g IR, activated charcoal should be administered ≤4 hours after ingestion. For massive MR cases, patients may benefit from treatment >4 hours after ingestion.

Modified-release

  • Acetylcysteine treatment should be started immediately if >200 mg/kg or 10g (whichever is lower) is ingested. (This is in accordance with the 2008 guideline).
  • Serial paracetamol concentrations, measured 4 hours apart, must be below the nomogram line and decreasing before acetylcysteine is discontinued.
  • Two hours before completion of acetylcysteine infusion, serum alanine aminotransferase (ALT) and paracetamol concentrations should be measured. Infusion should be continued if the ALT level is increasing (>50 U/L) or the paracetamol concentration is >10 mg/L (66 mmol/L).

Large or massive overdoses

  • Patients who have paracetamol concentrations >2 times the nomogram line may have decreased clearance and increased risk of hepatotoxicity, despite treatment. In these cases, modification of the acetylcysteine dose may be beneficial.
  • Although the optimal dose in these patients is not known, one approach is to double the concentration of the 16-hour infusion of acetylcysteine from 100 mg/kg (current standard third-bag infusion) to 200 mg/kg. Serum ALT and paracetamol concentrations should be measured near completion of the infusion. If ALT is >50 U/L or paracetamol concentration >10 mg/L, acetylcysteine should be continued.
  • The Poisons Information Centre or a clinical toxicologist may be consulted for the most current advice on managing these patients, including the optimal acetylcysteine regimen.

Liquid paracetamol ingestion in children <6 years

  • When it is suspected that >200 mg/kg has been ingested by a child <6 years of age, serum paracetamol concentration should be measured ≥2 hours after ingestion.
  • If, at 2 to 4 hours after ingestion, concentration is <150 mg/L (1000 mmol/L) acetylcysteine is not required. If the 2-hour concentration is >150 mg/L, it should be measured again after a further 2 hours and acetylcysteine started if the value is still >150 g/L, as per the paracetamol nomogram.
  • In all other cases, such as children who present later than 4 hours after ingestion, and children who are older than 6 years of age, treatment is the same as that for acute paracetamol exposure in adults.

Repeated supratherapeutic ingestion

  • If patients meet the criteria for supratherapeutic ingestion, they should have paracetamol and ALT concentrations measured.
  • The main changes from the previous guideline concern criteria for assessment in those who have ingested >100 mg/kg/day or 4 g/day (whichever is lower) per 24-hour period for >48 hours.
  • Patients only require assessment if they have symptoms such as abdominal pain or nausea or vomiting.