Activated Charcoal in Paracetamol Poisoning
Activated charcoal should be administered at 1 g/kg orally (standard adult dose 50g) if the patient presents within 1-2 hours of paracetamol ingestion, and it can still provide benefit up to 3-4 hours post-ingestion. 1
Timing and Dosing
- Optimal window: Administer activated charcoal within the first hour of ingestion for maximum efficacy 2, 3
- Extended benefit window: Can still be beneficial up to 3-4 hours after ingestion 1
- Standard dosing: 1 g/kg body weight as a slurry in water (50g for adults) 1
- The charcoal-to-drug ratio of 10:1 remains the recommended standard, as lower ratios (such as 5g doses) show significantly reduced efficacy with 59% larger paracetamol AUC compared to standard dosing 4
Critical Clinical Considerations
Activated charcoal administration does NOT interfere with subsequent N-acetylcysteine (NAC) therapy, so do not delay NAC if charcoal was just given 1. This is particularly important because:
- Gastrointestinal decontamination becomes especially valuable when NAC cannot be administered within 8 hours of ingestion 2
- NAC remains the definitive antidote and should be started based on standard nomogram criteria regardless of charcoal administration 1
Contraindications and Safety
Activated charcoal should NOT be given when:
- Patient has impaired consciousness without a secured airway (aspiration risk) 5
- Active gastrointestinal bleeding is present 6
- Risk of gastrointestinal perforation exists 6
The patient must be fully conscious and capable of swallowing safely before administration 7
Formulation Cautions
- Use sorbitol-containing formulations cautiously, as hypernatremic dehydration has been reported with repeated doses 8, 6, 9
- Administer as a slurry in water 6
Special Scenarios
For repeated supratherapeutic ingestions (RSTI) of paracetamol:
- Gastrointestinal decontamination is NOT needed 2
- Focus should shift entirely to NAC therapy based on cumulative dose assessment
For modified-release paracetamol:
- Activated charcoal can be given up to 6 hours post-ingestion due to delayed absorption 5
- All potentially toxic ingestions (≥10g or ≥200 mg/kg) require full NAC course 3
Evidence Quality Note
The 2005 AASLD guideline 1 and 2020 Australian/New Zealand guidelines 3 provide the strongest evidence base, both emphasizing early charcoal administration while clarifying it does not compromise antidote therapy. The 2006 consensus guideline 2 supports prehospital use within 2 hours when local protocols permit, though this requires careful patient selection to avoid aspiration risk.