Overdose and Poisoning

Question 1

Which groups of patients are at an increased risk of developing hepatotoxicity following a paracetamol overdose?

Answer 1

• Patients taking liver enzyme-inducing drugs (rifampicin, phenytoin, carbamazepine, chronic alcohol XS, St John’s Wort)
• Malnourished patients (eg. anorexia nervosa) or patients who have not eaten for a few days

Acute alcohol intake, as opposed to chronic alcohol XS, is not associated w/ increased risk of developing hepatotoxicity + may actually be protective

Question 2

Paracetamol overdose: What is the management for those presenting within 4 hours of ingestion?

Answer 2

• < 1 hr → activated charcoal if more than 150 mg/kg ingested
• Measure plasma conc @ 4hrs post ingestion; if levels above treatment line, give N-acetylcysteine IV using following regimen:
  
  • 1^st infusion → 150mg/kg (max 16.55g) in 200mL 5% glucose as IV infusion over 60 mins
  • 2^nd infusion → 50mg/kg (max 5.5g) in 500mL 5% glucose as IV infusion over next 4hrs
  • 3^rd infusion → 100mg/kg (max 11g) in 1L 5% glucose as IV infusion over next 16hrs

Question 3

Paracetamol overdose: What is the management for those presenting within 4-8 hours of ingestion?

Answer 3

• Measure plasma paracetamol concentrations at presentation
• Compare concentrations with treatment graph to determine if need treatment

Question 4

Paracetamol overdose: What is the management for those presenting within 8-15 hours of ingestion?

Answer 4

• Take blood for urgent measurement of plasma paracetamol concentrations
• Start N-acetylcysteine infusion immediately if more than 150mg/kg of paracetamol ingested
• Stop treatment if level is below the treatment line

Question 5

Paracetamol overdose: What is the management for those presenting within 15-24 hours of ingestion / staggered overdose?

Answer 5

• Take blood for urgent measurement of plasma paracetamol concentrations
• Start N-acetylcysteine infusion immediately

*an overdose is considered staggered if all the tablets were not taken within 1 hour

Question 6

What is the King’s College Hospital criteria for liver transplantation due to paracetamol liver failure?

Answer 6

• Arterial pH < 7.3 @ 24 hrs after ingestion

OR all of the following:

• PT time > 100 seconds
• creatinine > 300 umol/l
• grade III or IV encephalopathy

Question 7

What are the clinical features of opioid overdose?

Answer 7

• Respiratory depression (RR < 8)
• Pin-point pupils
• Coma / drowsiness
• Confusion
• Hallucinations
• Myoclonic jerk

Question 8

What is the management of opioid overdose?

Answer 8

• Stop opioid + establish vital signs monitoring
• ABCDE approach
• Give NALOXONE by IV injection 100-200mcg every 2-3 mins, until the patient is rousable and respiratory drive returns - expect to see an improvement after 3-4 doses