GI: Paracetamol OD

Question 1

What is the most common patient presentation of a paracetamol overdose?

Answer 1

Initially, most patients are asymptomatic or have mild GI symptoms. W/o treatment patients may have varying degrees of liver injury

Rarely, in massive overdose, patient may be in coma and have severe metabolic acidosis

Question 2

What is the recommended dose of paracetamol in adults?

Answer 2

4g in 24 hours

Question 3

What are the different types of paracetamol overdose?

Answer 3

Acute overdose- excessive amount of paracetamol taken in 1 hour or less, usually context of self harm

Staggered overdose- excessive amount of paracetamol taken in over 1 hour, usually in context of self harm

Therapeutic excess- Excessive paracetamol taken with intent to treat pain/fever no self harm intent. Ingested at a dose greater than licensed daily dose AND more than or equal to 75mg/kg/24hours

Question 4

Aside from being asymptomatic, what other features may a patient with a paracetamol overdose present with?

Answer 4

N&V
RUQ pain
jaundice
hepatomegaly
loin pain
altered conscious

Question 5

What are the risk factors for paracetamol overdose?

Answer 5

History of self harm
Hx of frequent or repeated use of medications for pain relief
Glutathione deficiency
Long term treatment with CYP450 inducers

Question 6

What are risk factors for glutathione deficiency?

Answer 6

Malnourishment
Eating disorders
Psychiatric disorders
Chronic illness
Cachexia
Alcohol-use disorder

Question 7

What are some examples of CYP450 inducers?

Answer 7

Carbamazepine
Phenytoin
Rifampicin
St John’s wort

Question 8

What investigations should you consider in a paracetamol overdose?

Answer 8

Serum paracetamol conc
LFTs- ALT may be raised in liver injury
Prothrombin time and INR- PT may be increased and INR may be raised
Blood glucose- hypoglycaemia may indicate acute liver injury
U&Es- creatine may be elevated-> indicative of AKI or acute liver injury (heptorenal syndrome)
VBG/ABG- may show lactic acidosis
FBC- may show leukocytosis, anaemia or thrombocytopenia

Question 9

How do you treat an acute single overdose of paracetamol?

Answer 9

<8hrs since the overdose: supportive care and If more than 150mg/kg of paracetamol activated charcoal

8-24hrs since overdose- supportive care and (consider) acetylcysteine

> 24hrs since ingestion- supportive care and (consider) acetylcysteine

Question 10

How you treat a staggered overdose of paracetamol?

Answer 10

Supportive care and acetylcysteine

Question 11

How do you treat a therapeutic overdose of paracetamol?

Answer 11

Supportive care and acetylcysteine

Question 12

How is acetylcysteine given?

Answer 12

3 sequential infusions over 1hr, 4 hrs and 16hrs

Question 13

Why do you get the toxic effects of paracetamol OD?

Answer 13

• glutathione accumulation

Question 14

Pt develops a rash and urticaria after starting acetylcysteine infusion. What do you do?

Answer 14

• Stop the infusion
• IV chlorphenamine
• Once symptoms resolves, restart infusion at a slower rate