Paracetamol Overdose

Causes hepatotoxicity. Management of acute overdoses is well defined; staggered overdoses or supratherapeutic ingestions are more complex — call a toxicologist/Poisons Information Centre (13 11 26) if concerned.

Toxic dose

Acute overdose (single dose, or staggered/multiple deliberate doses taken over more than 2 hours):

• 10 g, or >200 mg/kg if the patient weighs <50 kg

• A staggered ingestion is still assessed on the nomogram, timed from the earliest dose — it is not the same as a repeated supratherapeutic ingestion (below), which does not use the nomogram at all

Repeated supratherapeutic ingestion (accidental or therapeutic-intent overuse over days, not a deliberate staggered overdose):

• 10 g in 24 hours

• 6 g/day for 48 hours

• 4 g/day with predisposing factors (e.g. alcohol misuse, malnutrition)

Paediatric accidental ingestion — a single accidental ingestion <200 mg/kg in an asymptomatic child can be managed with parental reassurance and avoiding further dosing for 24 hours, without testing. Intentional self-poisoning always warrants hospital referral for serum paracetamol measurement, regardless of the stated dose.

Clinical presentation (acute)

• Nausea, vomiting, RUQ pain
• Hepatic/renal failure
• Mild coagulopathy

Treatment

N-acetylcysteine (NAC) should be started within 8 hours of an acute overdose, using the two-bag regimen: 200 mg/kg over 4 hours, then 100 mg/kg over 16 hours.

• For a single acute ingestion, use the paracetamol nomogram (check units before plotting) to decide on NAC.

  

• Do not use the nomogram for repeated supratherapeutic ingestion (a staggered deliberate overdose still uses it, timed from the earliest dose). Instead, treat if transaminases are elevated or paracetamol level >132 micromol/L.

From eTG.