Acetaminophen (Paracetamol) Poisoning — Management Pathway

Step-by-step decision

Choose step by step as prompted; reaching an endpoint gives the management recommendation. You can go back a step or restart anytime.

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Full pathway

1. [Decision] Dose & timing assessment
   What is the ingestion situation? (An acute single ingestion ≥150 mg/kg (about 7.5–10 g in an adult) carries toxicity risk. Confirm the time of ingestion (needed for the nomogram). Early (<1–2 h, especially large ingestions) activated charcoal may be used.)
   • Known time, 4 h level obtainable → Level vs nomogram
   • Unknown time / staggered / late large ingestion → Unknown time/staggered → empiric NAC
2. [Decision] Level vs nomogram
   Is the ≥4 h level at or above the treatment line? (Measure the acetaminophen level ≥4 h post-ingestion; the nomogram treatment line (US: 150 µg/mL [993 µmol/L] at 4 h → 4.7 µg/mL at 24 h). The nomogram applies only to a single acute ingestion with a known time.)
   • At or above the treatment line → Start NAC
   • Below the line and asymptomatic → Below the treatment line
3. [End] Below the treatment line
   Level below the treatment line, asymptomatic and normal transaminases: NAC usually not needed; medically clear and discharge with observation and return advice. Extended-release formulations need repeat levels at 4/6/8 h before deciding.
4. [End] Start NAC
   Start N-acetylcysteine (NAC): give it once the level is at or above the treatment line. NAC given <8 h is almost 100% hepatoprotective (equivalent 0–8 h), but it should still be given late. IV 21-h regimen (150 mg/kg loading over 1 h → 50 mg/kg over 4 h → 100 mg/kg over 16 h) or the oral 72-h regimen. Monitor transaminases, INR, renal function; if progressing to liver failure, transfer to a transplant center per King's College criteria.
5. [End] Unknown time/staggered → empiric NAC
   The nomogram does not apply: start NAC empirically as early as possible (detectable acetaminophen, or raised AST/ALT, or a definite large ingestion), with serial levels and liver function for dynamic assessment. Transfer to ICU if liver injury, metabolic acidosis, coagulopathy or encephalopathy appear.

Source guidelines & references

• Rumack-Matthew nomogram for acetaminophen poisoning (single acute ingestion)
• ACEP / MSD Manual: acetaminophen poisoning and NAC regimens

This pathway is our own synthesis of the decision logic in the guidelines above (not the guideline verbatim); thresholds and workflows change as guidelines update — in practice follow the latest guideline, your institution's protocol and the individual patient.

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