What is the recommended dosing of N-acetylcysteine (NAC) for acetaminophen overdose in pediatric patients?

N-acetylcysteine Dosing for Pediatric Acetaminophen Overdose

The recommended dosing of N-acetylcysteine (NAC) for acetaminophen overdose in pediatric patients is a loading dose of 150 mg/kg IV over 15-60 minutes followed by maintenance doses totaling 300 mg/kg over 21 hours. 1

Standard IV NAC Dosing Regimen

The FDA-approved regimen for intravenous NAC administration in pediatric patients consists of a 3-bag method:

1. Loading dose: 150 mg/kg IV over 15-60 minutes
2. Second dose: Followed by maintenance doses
3. Third dose: Total recommended dosage of 300 mg/kg given over a total infusion time of 21 hours 2

This weight-based dosing is the same for both adults and pediatric patients, with no adjustment needed based on age alone.

Alternative Regimens

Some institutions use a simplified two-stage infusion regimen:

• 150 mg/kg loading dose over 1 hour
• Followed by continuous infusion of 10 mg/kg/hour for 20 hours 3

This alternative regimen may reduce the risk of medication errors associated with the traditional 3-bag method while maintaining efficacy. A retrospective study of this approach in pediatric patients showed favorable outcomes with only 3.4% developing hepatotoxicity and no patients developing hepatic failure 4.

Solution Considerations

NAC is hyperosmolar (2600 mOsmol/L) and must be diluted prior to administration. For pediatric patients, appropriate dilution is crucial:

• Can be diluted in sterile water for injection, 0.45% sodium chloride, or 5% dextrose
• For pediatric patients, ensure the osmolarity is physiologically safe (generally not less than 150 mOsmol/L) 2
• Using 0.45% saline with 5% dextrose has been shown to help prevent symptomatic hyponatremia in children 3

Treatment Duration and Monitoring

The standard treatment duration is 21 hours, but should be extended in cases where:

• Acetaminophen levels are still detectable after completion of the standard regimen
• ALT/AST levels are still increasing
• INR remains elevated 2

Monitor the following throughout treatment:

• Hepatic function (ALT, AST, bilirubin)
• Renal function
• Coagulation parameters (INR)
• Electrolytes
• Mental status 1

Special Considerations

For massive acetaminophen overdoses (levels above the "300-line" on the Rumack-Matthew nomogram), higher NAC doses may be necessary, as these patients develop hepatotoxicity at higher rates 5.

Adverse Effects

Be aware of potential hypersensitivity reactions:

• Acute flushing and erythema (common, occurring 30-60 minutes after starting infusion)
• More severe reactions including rash, hypotension, wheezing, and shortness of breath
• Use with caution in patients with asthma or history of bronchospasm 2

Early administration of NAC (within 8 hours of ingestion) is critical for preventing morbidity and mortality, with only 1% of patients developing severe hepatotoxicity when treated within this timeframe 1.