Paracetamol Overdose

Question 1

What is the active ingredient in paracetamol which causes the overdose?

Answer 1

Acetaminophen

Question 2

What is the most common overdose in the UK?

Answer 2

Paracetamol

Question 3

What causes the toxicity from paracetamol?

Answer 3

• An intermediate reactive metabolite binds covalently to cellular proteins
  
  • Causing cell death
• Results in hepatic failure
• In therapeutic doses, the toxic metaboilte is detoxified in reactions involving glutathione
• In overdose, glutathione reserves become exhausted

Question 4

Describe the managment of someone who has had a paracetmol overdose?

Answer 4

• Patients presenting within 1 hour:
  
  • Activated charcoal: reduces paracetamol absorption
• Within 8 hours of overdose:
  
  • Acetylecysteine IV
• Alternative: Methionine PO
  
  • 4 doses, 4 hours apart

Question 5

Draw a paracetamol nomogram

Answer 5

• Above the line - Treat with n-acetylcysteine
  
  • Benefits of treatment outweight risk
• Below the line
  
  • Risk outways benefits of treatment

Question 6

When do you stop treating paracetamol overdose?

Answer 6

• If the paracetamol concentration is below the nomogram treatment line
• Liver/renal function, INR and venous bicarbonate can also be monitored

Question 7

Side effects of acetylcysteine?

Answer 7

• Anaphylactic reactions
  
  • Related to dose-related histamine release
  • Itch, urticaria, bronchospasm, hypotension
• Managed with temporary acetylcysteine cessation and anti-histamine adminstration

Question 8

Describe a staggered overdose of paracetamol and its management?

Answer 8

• If multiple ingestions of paracetamol have taken place over several hours
• Acetylcysteine is indicatedf

Question 9

Describe the King’s College London criteria for liver transplantation for paracetamol overdose?

Answer 9

• Arterial pH <7.3, 24 hours after ingestion
• OR
• All of the following:
  
  • PT > 100 seconds
  • Creatinine > 300
  • Grade III or IV encephalopathy