Paracetamol poisoning

12g (=24 tablets) or 150mg/kg in adults may be fatal. If the patient is malnourished then 75mg/kg can kill.

If the patient weighs >110kg, calculate ingested dose using a body weight of 110kg to avoid underestimating toxicity.

Investigations

• Glucose
• Urea, Creatinine
• Electrolytes
• Liver Function Tests
• INR
• ABG
• CBC
• HCO3
• Blood paracetamol level at 4h post-ingestion.

Management

1. General measures: (See Acute poisoning article—general measures).
2. GI decontamination is recommended in those presenting <4h after overdose: give activated charcoal 1g/kg (max 50g).
3. If <10–12h since overdose, not vomiting start acetylcysteine.
4. If >8–24h and suspicion of large overdose (>7.5g) err on the side of caution and start acetylcysteine, stopping it if level below treatment line and INR/ALT normal.
5. If ingestion time is unknown, or it is staggered, or presentation is >15h from ingestion, treatment may still help. (Get advice).
6. Acetylcysteine is given by IVI: 150mg/kg in 5% glucose over 15–60min; then 50mg/kg in 500mL of 5% glucose over 4h; then 100mg/kg/16h in 1L of 5% glucose.
7. Rash is a common SE: treat with chlorphenamine + observe; do not stop unless anaphylatoid reaction with shock, vomiting, and wheeze (occur <10%).
8. An alternative (if acetylcysteine unavailable) is methionine 2.5g/4h oral for 16h (total: 10g), but absorption is unreliable if vomiting.

Ongoing management

• Next day do INR, Urea, Creatinine, Electrolytes, Liver Function Tests.
• If INR rising, continue acetylcysteine until <1.4.
• If continued deterioration, discuss with the liver team. Don’t hesitate to get help.
• Consider referral to specialist liver unit guided by e.g. King’s College criteria.

King’s College Hospital criteria in paracetamol-induced acute liver failure

• Arterial pH <7.3 24h after ingestion

Or all of the following

• Prothrombin time (PT) >100s
• Creatinine 3.4 mg/dL
• Grade III or IV encephalopathy.

Fulfilling these criteria predicts poor outcome in acute liver failure