Acetaminophen Poisoning (Paracetamol Overdose)

The minority of patients who present within 1 hour may benefit from activated charcoal to reduce absorption of the drug.

Acetylcysteine should be given if:

• the plasma paracetamol concentration is on or above a single treatment line joining points of 100 mg/L at 4 hours and 15 mg/L at 15 hours, regardless of risk factors of hepatotoxicity
• there is a staggered overdose (i.e. not taken all within 1 hr) or there is doubt over the time of paracetamol ingestion, regardless of the plasma paracetamol concentration; or
• patients who present 8-24 hours after ingestion of an acute overdose of more than 150 mg/kg of paracetamol even if the plasma-paracetamol concentration is not yet available
• patients who present > 24 hours if they are clearly jaundiced or have hepatic tenderness, their ALT is above the upper limit of normal
  • acetylcysteine should be continued if the paracetamol concentration or ALT remains elevated whilst seeking specialist advice

Acetylcysteine is now infused over 1 hour (rather than the previous 15 minutes) to reduce the number of adverse effects. Acetylcysteine commonly causes an anaphylactoid reaction (non-IgE mediated mast cell release). Anaphylactoid reactions to IV acetylcysteine are generally treated by stopping the infusion, then restarting at a slower rate.

King's College Hospital criteria for liver transplantation (paracetamol liver failure)

Arterial pH < 7.3, 24 hours after ingestion

or all of the following:

• prothrombin time > 100 seconds
• creatinine > 300 µmol/l
• grade III or IV encephalopathy