Paracetamol Overdose

Question 1

How much paracetamol is usually considered fatal?

Answer 1

12g (24 tablets) or 150mg/kg

This gives 12g in a person of 80kg.

Question 2

How should paracetamol overdose be calculated in patients

> 110kg?

Answer 2

Calculate ingested dose using a body weight of 110kg to avoid underestimating toxicity.

Do not use a weight over 110kg, just use 110.

Question 3

What is a fatal dose for a malnourished patient?

Answer 3

75mg/kg, sometimes more, sometimes less.

Question 4

Signs and symptoms of paracetamol overdose.

Answer 4

None initially or there might be vomiting and RUQ pain

Later on jaundice and encephalopathy will develop

Also AKI

Question 5

General management algorithm for poisoning.

This is not solely due to paracetamol.

Answer 5

1 - ABC, clear airways

2 - Consider ventilation if resp. is < 8 minutes or PaO2 < 8 kPa-

3 - Treat any shock

4 - If unconscious, nurse semi-prone

5 - Assess the patient again

6 - Take a history from patient, family or friends.

7 - Examination

8 - Ix = Glucose, U&Es, FBCs, LFTs, INR, ABG, ECG, paracetamol, and salicylate levels.
Urine/serum toxicology, specific assays as appropriate

9 - Basic BLOs

10 - Supportive measures
Consider gastric lavage +/- activated charcoal.

11 - Do specific measures

Question 6

Managements that can be done in paracetamol poisoning.

Answer 6

GI decontamination - Activated charcoal

Acetylcysteine

Methionine (if acetylcysteine is unavailable)

Question 7

When should activated charcoal be given?

Answer 7

In those presenting < 4h after their overdose.

Activated charcoal should be given 1g/kg and max 50g.

Activated charcoal binds to paracetamol and prevents further absorption of paracetamol.

This means that if it is given later than 4h it won’t have much of an effect because all the paracetamol has already been absorbed.

Question 8

Monitoring of paracetamol overdose.

Answer 8

Glucose

U&Es

LFTs

INR

ABG

FBC

HCO3-

Blood paracetamol level at 4h post-ingestion

Question 9

If < 10-12h has gone and there is no vomiting, but the paracetamol is above the treatment line,

What should be done?

Answer 9

Start acetylcysteine

Question 10

Explain the treatment line graph.

Answer 10

If you have a plasma-paracetamol concentration above the treatment line at any time, acetylcysteine should be given.

Question 11

If > 8h-24h since overdose but there is suspicion of a large overdose (>7.5g). What should be done?

Answer 11

On the side of caution start acetylcysteine.

Stop acetylcysteine if the paracetamol level is below the treatment line and INR/ALT are normal.

Question 12

What to do if the ingestion time is unknown or staggered or presentation is >15h from ingestion?

Answer 12

Treatment may still help

Get senior help as well.

Question 13

Explain the administration of acetylcysteine.

Answer 13

It is given IVI.

150mg/kg in 5% glucose over 15-60 min

Then 50mg/kg in 500ml of 5% glucose over 4h

Then 100mg/kg/16h in 1L of 5% glucose.

Question 14

Common side effect of acetylcysteine.

Answer 14

Rash

Question 15

Treatment of side-effects of acetylcysteine.

Answer 15

Chlorphenamine + observe

Do not stop acetylcysteine treatment unless there is an anaphylactic reaction with shock, vomiting and wheeze.

Question 16

Ongoing management of paracetamol overdose.

Answer 16

Next day do INR, U&Es, LFTs. If INR is still rising continue acetylcysteine until < 1.4

If continued deterioration discuss with the liver team and get senior help.

Consider referral to specialist liver unit guided by e.g. King’s College criteria