A 4-year-old (15 kg) is brought 3 hours after ingesting approximately 20 tablets of paracetamol (500 mg each). She is asymptomatic. Serum paracetamol level is 220 μg/mL drawn at 4 hours post-ingestion. According to the Rumack-Matthew nomogram, which of the following is the most appropriate next step?
- A Observe and repeat paracetamol level at 8 hours
- B Start N-acetylcysteine (NAC) immediately ✓
- C Administer activated charcoal 1 g/kg
- D Administer oral methionine as antidote
Correct answer: B. Start N-acetylcysteine (NAC) immediately
Explanation
The Rumack-Matthew nomogram plots serum paracetamol level against time since ingestion. A level of 220 μg/mL at 4 hours is well above the treatment line (150 μg/mL at 4 hours in the original nomogram). NAC is indicated and most effective within 8 hours. Activated charcoal is only useful within 1-2 hours. Observation alone would be dangerous as the level is in the toxic range.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.