What is the modified SNAP NAC protocol?

SNAP 2-bag protocol: 200 mg/kg in 200 mL 5%DW over 4h, then 100 mg/kg in 1000 mL 5%DW over 16h (total 300 mg/kg over 20h); 20% lower anaphylactoid reaction rate vs standard 3-bag protocol (Prescott); equivalent hepatoprotection; preferred in many centers.

What is the standard Prescott 3-bag NAC protocol?

Bag 1: 150 mg/kg in 200 mL 5%DW over 15-60 min (loading); Bag 2: 50 mg/kg in 500 mL over 4h; Bag 3: 100 mg/kg in 1000 mL over 16h; total 300 mg/kg over 21h; maximum single bag dose capped at 100 mg/kg (for patients <40 kg or morbid obesity).

What anaphylactoid reactions occur with IV NAC?

Anaphylactoid reactions in 5-15% (Prescott) vs 1-5% (SNAP/modified regimens); symptoms: flushing, urticaria, bronchospasm, hypotension; occur predominantly during first bag (loading dose); treat with stopping infusion + antihistamine ± epinephrine; restart at slower rate after resolution.

Can oral NAC replace IV NAC?

Oral NAC 140 mg/kg loading then 70 mg/kg q4h for 17 doses is equivalent for low-risk uncomplicated APAP overdose; IV preferred for: vomiting, altered mental status, pregnancy, severe hepatotoxicity; IV achieves higher plasma levels faster.

When should NAC be extended beyond standard 21-hour protocol?

Extended NAC indicated: severe hepatotoxicity (ALT >3000 IU/L rising), coagulopathy (INR >2), encephalopathy, ALT not declining at 20-24h; continue at 6.25 mg/kg/h until AST/ALT improving and INR <2; consult liver transplant team if King’s College Criteria met.

IV N-Acetylcysteine (NAC) SNAP Protocol and Anaphylactoid Risk

Calculates the modified SNAP (Simplified N-Acetylcysteine Protocol) for acetaminophen toxicity with lower anaphylactoid reaction rate, and standard 21-hour Prescott protocol comparison with weight-capped dosing.

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Frequently Asked Questions

What is the modified SNAP NAC protocol?

What is the standard Prescott 3-bag NAC protocol?

What anaphylactoid reactions occur with IV NAC?

Can oral NAC replace IV NAC?

When should NAC be extended beyond standard 21-hour protocol?