Paracetamol Overdose Flashcards
what is the recommended dose of paracetamol for an adult
4g or 75mg/kg in 24hours
what is the definition of a paracetamol overdose
> 4g or >75mg/kg in 24hours
what is the definition of hepatotoxicity after a paracetamol overdose
AST >1000IU/L
what is the most common drug taken for intentional overdoses
paracetomal
epi
self-harm/suicide
what is a risk factor for paracetamol overdose due to self-medication
dental pain
what are the common causes of paracetamol overdose
self harm attempt
therapeutic error
pathophysiology
with a NORMAL dose, paracetamol is metabolised and non-toxic metabolites are secreted in the urine
a small proportion of paracetamol is metabolised by cytochromes P450 to toxic NAPQI
with a small amount of toxic NAPQI, it combines with glutathione and becomes non toxic and is excreted in the urine
in OVERDOSES of paracetamol, when too much toxic NAPQI is produced, it binds to cellular components and causes hepatocyte injury and death leading to acute liver failure
which cytochrome P450 is associated with paracetamol metabolism
CYP2E1
risk factors
COMAH
Chronic alcoholics
On drugs which are P450 inducers (carbamazepine)
Malnourished or Mental Health problems (self harm) or Medication use
Anorexia
HIV patients
what are features of paracetamol overdose
Hx of self harm of repeated pain relief medications
patients who present in the first 24hrs will often be asymptomatic
N+V + abdominal pain typically presents 2-3days after ingestion
when does hepatotoxicity peak
2-3days post ingestion (N+V + abdominal pain)
what signs may be visible with paracetamol overdose
RUQ + tenderness
jaundice
signs of liver failure (coma, confusion, consciousness decreased)
investigations
bloods
- serum paracetamol levels
- AST and ALT levels
- prolonged PT and INR with liver failure
what is the first line investigation for paracetamol overdose
serum paracetamol levels
