Paracetamol overdose

Question 1

Define paracetamol overdose?

Answer 1

ingestion of paracetamol over the recommended dose (4g (75mg/kg) in 24 hours)

Question 2

What is a staggered overdose?

Answer 2

ingestion of multiple doses of paracetamol over the period of over an hour
The definition of hepatotoxicity after paracetamol overdose is a serum AST concentration at least 1000 IU/L

Question 3

Aetiology of paracetamol overdose?

Answer 3

• Usually occurs as a self-harm attempt or a therapeutic error
o Self-harm: ingestion of a large amount
o Therapeutic error: repeated ingestion of smaller amounts
 May arise from ingesting multiple formulas containing paracetamol
 Possible with children with incorrect dosing by parents
 Elderly
 Chronic liver pathology

Question 4

Risk factors for paracetamol overdose?

Answer 4

• History of self-harm
• History of frequent medications
• Glutathione deficiency
• CYP450 inducers – e.g. phenobarbital

Question 5

Epidemiology of paracetamol overdose?

Answer 5

• Most frequently used drug in intentional overdoses in UK
o 48% of poisoning admissions
o 100-200 deaths per year
• Incidence of poisoning has decreased for all types of self-harm
• 1% mortality rate
• Majority of overdoses occurring in young women
• Increasing number of iatrogenic poisoning with IV paracetamol

Question 6

Presenting symptoms in the first 24h of overdose?

Answer 6

NONE

Question 7

Presenting symptoms after 24h?

Answer 7

• Nausea and vomiting
• Abdominal pain
• RUQ pain and tenderness

Question 8

Presentation of overdose?

Answer 8

• Most will present immediately after an accidental ingestion or inhalation of a known drug or chemical.
• Some may present later — such as parents (unaware at the time of poisoning) presenting with children, and people (or their friends or relatives) who have intentionally poisoned themselves.
• A minority may be found unconscious by someone else following a poisoning episode.
• One may be asymptomatic or have only vague symptoms and signs in the early stages of poisoning.

Question 9

Signs of paracetamol overdose on examination?

Answer 9

• Attempted self-harm
• Repeated non-prescription analgesic use for pain relief
• Jaundice
• Confusion/decreased consciousness

Question 10

First line investigations for overdose?

Answer 10

o	*Serum paracetamol*
	May or may not be positive
	Assess treatment efficacy
o	*Serum AST and ALT*
	May be elevated
	At initial presentation, then throughout management
o	*Arterial pH and lactate*
	Severity of hepatic failure
o	Urea and electrolytes
	Renal impairment
o	Serum prothrombin time
	May be prolonged

Question 11

Which drug treats an overdose?

Answer 11

N-acetyl cysteine