Paracetamol Overdose

Paracetamol Overdose: What is the pathophysiology?

Build up of toxic NAPQI metabolite due to depletion of glutathione stores

Paracetamol Overdose: What is the classification?

• Acute→ less than 1 hour

• Staggered→ more than 1 hour

• Therapeutic→ by accident, more than 75mg/kg/24 hours

Paracetamol Overdose: What are the signs and symptoms?

• Nausea and vomiting

• 72 hrs→ RUQ pain + hypotension

• 72-96 hrs→ Metabolic acidosis

• Confusion, drowsiness, jaundice etc.

Paracetamol Overdose: Why is salicylate levels tested?

To look for a mixed overdose with aspirin

Paracetamol Overdose: What is the management?

• Ingestion less than 1 hour ago + dose >150mg/kg: Administer activated charcoal

• Ingestion 1-4 hours ago: Wait until 4 hours to take a level and treat with N-acetylcysteine (NAC) based on level

• Ingestion within 4-8 hours + dose >150mg/kg: Start NAC immediately if there is going to be a delay of >8 hours in obtaining the paracetamol level, otherwise wait for level and treat if level high (above the treatment line on the nomogram)

• Ingestion within 8-24 hours + dose >150mg/kg: Start NAC immediately

Summary → if less than 1 hour ago = charcoal, more than 1 hour ago = NAC

Paracetamol Overdose: What is the drug MOA of NAC (N-acetylcysteine)?

NAC is given as an IV medication - it acts by increasing glutathione levels thereby preventing toxicity:

• Standard regimen of 3 consecutive infusions totalling 21 hours in duration

• The newer SNAP protocol (now recommended by Royal College of Emergency Medicine as standard) where the same dose of NAC is given over 12 hours in two infusions