PARACETAMOL POISONING

Question 1

Investigations in paracetamol poisoning

Answer 1

Serum paracetamol concentration
Baseline liver function tests (AST, ALT, total bilirubin),
PT and INR
Urea and electrolytes

Question 2

In all patients with a suspected intentional overdose, obtain the following:

Answer 2

Serum salicylate concentration
Serum glucose
ECG
Pregnancy test in women of childbearing age

Question 3

Treatment regimen in paracetamol overdose

Answer 3

1. Secure airway, breathing, and circulation as necessary
2. Give activated charcoal (AC)
3. Treat with N-Acetylcysteine (NAC)

Question 4

Dosage regimen of activated charcoal given in paracetamol overdose

Answer 4

50 g to all adult patients presenting within 4 hours of ingestion, unless contraindicated;

Question 5

Can activated charcoal be used beyond 4 hours of paracetamol ingestion

Answer 5

AC may be useful for co-ingestants beyond 4 hours

Question 6

When is NAC used in paracetamol overdose

Answer 6

1. Serum paracetamol concentration drawn at 4 hours or more after a single acute
   ingestion is above the “treatment” line of the treatment nomogram for paracetamol
   poisoning
2. Serum paracetamol concentration is unavailable or will not return within 8 hours of
   time of ingestion and paracetamol ingestion is suspected
3. Time of ingestion is unknown and serum paracetamol level is greater than 10
   microgram/ml (66 micromol/L)
4. There is evidence of any hepatotoxicity with a history of paracetamol ingestion
5. Repeated excessive paracetamol ingestions, risk factors for paracetamol-induced liver damage and serum
   paracetamol concentration is greater than 10 microgram/ml (66 micromol/L)

Question 7

When is oral dosing of NAC used

Answer 7

non-pregnant patients with a functional GI tract and no
evidence of hepatotoxicity

Question 8

Oral dosing of NAC

Answer 8

Dose 140 mg/kg loading dose, followed by 17 doses of 70 mg/kg every 4 hours

Question 9

If vomiting occurs within 1 hour of oral NAC dosing, what should be done

Answer 9

A full NAC dose should be repeated as rapidly as possible

Question 10

When is therapy terminated for oral NAC

Answer 10

By 24 to 36 hours after ingestion if the paracetamol level is below 10 micrograms/ml, and the patient does not develop evidence of hepatotoxicity and remains clinically well

Question 11

IV NAC dosing regimen in patients without biochemical evidence of liver failure

Answer 11

Use 21 hour IV protocol: 150 mg/kg loading dose over 60 minutes, followed by 50 mg/kg
infused over 4 hours, with the final 100 mg/kg infused over the remaining 16 hours

Question 12

IV NAC dosing regimen in patients with biochemical evidence of liver failure

Answer 12

Administer the 21 hour IV protocol (150 mg/kg loading dose over 60 minutes, followed by 50 mg/kg infused over 4 hours, followed by 100 mg/kg infused over the next 16 hours)
Then
Follow with a continuous IV NAC infusion at 6.25 mg/kg per hour until INR is < 2

Question 13

Biochemical evidence of liver failure in paracetamol toxicity

Answer 13

INR>2

Question 14

Antiemetic therapy in paracetamol overdose

Answer 14

IV metoclopramide 10 mg 8 hourly

Question 15

When is IV route used for NAC administration

Answer 15

1. Can be used in all cases of paracetamol toxicity
2. Patients unable to tolerate oral NAC (e.g., intractable vomiting),
3. Patients with a medical condition precluding oral NAC (eg, corrosive ingestion, GI bleed)
4. Patients with significant hepatotoxicity (INR >2)
5. Pregnant patients