Paracetamol overdose

Question 1

Define

Answer 1

excessive ingestion of paracetamol causing toxicity

Maximum dose: Two 500mg tablets four times in 24h

Overdose: 150mg/kg or 12g in adults may be fatal (75mg/kg if malnourished)

Question 2

Causes

Answer 2

MAX recommended dose: 2 x 500 mg tablets, 4 x in 24 hrs

Intake > 12 g can cause hepatic necrosis

Question 3

Risk Factors

Answer 3

• Chronic alcohol abusers
• Pts on enzyme inducing drugs (↑cytochrome P450

activity) - such as anti-convulsants or anti-TB drugs

• Malnourishment, anorexia nervosa
• HIV more susceptible

Overdose often associated with injection of other substances (e.g. alcohol)

Question 4

Epidemiology

Answer 4

Most common intentional drug overdose in UK

70,000/ODs year, causing 100 deaths/year F>M

Death rate reduced by legislation in 1998 restricting pack sizes

Question 5

Causes

Answer 5

Make sure you ascertain the TIMING and QUANTITY of overdose and presence of risk factors

0-24 hrs

• ASYMPTOMATIC
• Mild nausea/vomiting
• Lethargy
• Malaise

24-72 hrs

• RUQ pain
• Vomiting

72+ hrs

• Increased confusion (encephalopathy)
• Jaundice

Question 6

Signs

Answer 6

0-24 hrs - no signs

24-72 hrs - liver enlargement and tenderness

72+ hrs - jaundice, coagulopathy, hypoglycaemia, renal angle tenderness

Only evident later in presentation

↘ Hepatomegaly and tenderness
↘ Jaundice, encephalopathy, hypoglycaemia↘ ±Acute kidney injury and renal angle pain↘ Coagulopathy

Question 7

Investigations

Answer 7

Measure paracetamol levels

NOTE: peak paracetamol levels are 4 hrs after ingestion

• FBC
• U&Es
• Glucose
• LFTs
• Clotting screen
• Lactate
• ABG