Acetylcysteine Pediatric Dose — Acetaminophen Toxicity

Acetylcysteine (N-acetylcysteine, NAC) is a sulfhydryl donor and glutathione precursor used as the primary antidote for acetaminophen (paracetamol) poisoning. It acts by replenishing hepatic glutathione stores, thereby neutralizing the toxic metabolite NAPQI and preventing hepatocellular injury. In pediatrics, it is indicated for acute acetaminophen overdose when serum levels fall within or above the treatment line on the Rumack-Matthew nomogram.

Pediatric Dosing

Acetylcysteine dosing should always be used in conjunction with the Rumack-Matthew nomogram to determine treatment necessity based on serum acetaminophen concentration and time post-ingestion.

Nasogastric (NG) Route

• Loading dose: 140 mg/kg NG once
• Maintenance dose: 70 mg/kg NG every 4 hours × 17 doses

Intravenous (IV) Route

• Loading dose: 150 mg/kg IV over 15 minutes
• First maintenance dose: 50 mg/kg IV over 4 hours
• Second maintenance dose: 100 mg/kg IV over 16 hours as a continuous infusion

Worked example for a 20 kg child (IV protocol):
Loading: 20 × 150 mg/kg = 3,000 mg over 15 min
Maintenance 1: 20 × 50 mg/kg = 1,000 mg over 4 hours
Maintenance 2: 20 × 100 mg/kg = 2,000 mg over 16 hours

Consult institutional protocol for maximum single doses, dilution volumes, and duration adjustments in patients with fulminant hepatic failure or ongoing ingestion.

Indications and Clinical Context

Acetylcysteine is the standard of care for acetaminophen poisoning, one of the most common pediatric toxic ingestions. Treatment efficacy is highest when initiated within 8–10 hours of ingestion; however, benefit has been demonstrated beyond this window, particularly in patients with evidence of hepatotoxicity. The Rumack-Matthew nomogram guides the decision to treat based on a serum acetaminophen level drawn at least 4 hours post-ingestion. Both the oral/NG 72-hour protocol and the IV 21-hour protocol are considered effective first-line regimens per standard toxicology and PALS-aligned guidelines.

The IV formulation is preferred when oral administration is not feasible due to vomiting, altered mental status, or co-ingestions requiring NG contraindication. The NG protocol may be appropriate in stable patients with intact airway protection and reliable gastrointestinal access.

Administration and Monitoring

For the IV protocol, each phase should be administered as a separate infusion, with careful attention to infusion rates to minimize anaphylactoid reactions, which are most common during the loading dose. Slow the infusion or temporarily stop if urticaria, bronchospasm, or hypotension occurs; most reactions resolve with rate reduction and antihistamine administration. The NG formulation is typically diluted to a 5% solution (from the 20% stock) in a sweet beverage to improve tolerability and reduce emesis.

• Route: NG or IV; choose based on clinical status and institutional resources
• Monitoring: Liver function tests (AST, ALT, bilirubin), INR, serum creatinine, and acetaminophen levels at baseline and serially
• Adverse effects: Nausea/vomiting (NG); anaphylactoid reactions including flushing, urticaria, and bronchospasm (IV loading dose)
• Contraindications: Known hypersensitivity to acetylcysteine; use caution in patients with asthma (IV route)
• Consult Poison Control or a clinical toxicologist for guidance on extended or modified protocols in complex cases.

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Disclaimer: This article is an educational reference summarizing standard pediatric dosing values. It is not a substitute for clinical judgment. Always verify doses against institutional protocols, the current edition of authoritative references (e.g., Lexicomp, Harriet Lane Handbook, PALS guidelines), the patient’s accurate weight, and any patient-specific factors (renal/hepatic function, allergies, comedications) before administration.