Tylenol Overdose Calculator
Calculate NAC antidote dosing and assess acetaminophen toxicity using Rumack-Matthew nomogram
NAC Antidote Dosing Calculator
THIS IS A LIFE-THREATENING EMERGENCY
Call Poison Control: 1-800-222-1222 or Emergency: 911
Time is critical - hepatotoxicity risk increases rapidly. This calculator is for healthcare professionals only.
Required for NAC dosing calculations
IV route is faster and more effective
Acetaminophen Toxicity Assessment
Nomogram valid for 4-24 hours post-ingestion
Clinical Example
Case: Adult Acetaminophen Overdose
Patient: 25-year-old, 70kg adult
History: Ingested 20g acetaminophen 6 hours ago
Lab: Acetaminophen level 180 mcg/mL at 6 hours
Assessment: Above treatment line (112.5 mcg/mL at 6h)
NAC Treatment (IV Protocol)
Loading dose: 10,500mg over 15 minutes
Second dose: 3,500mg over 4 hours
Third dose: 7,000mg over 16 hours
Total duration: 21 hours
Emergency Protocol
Immediate Actions:
- • Call Poison Control: 1-800-222-1222
- • Obtain stat acetaminophen level
- • Start NAC if indicated (don't wait for level)
- • Monitor liver function (AST, ALT, PT/INR)
- • Consider activated charcoal if <4 hours
Time-Critical Factors:
- • Most effective within 8 hours
- • Can be effective up to 24 hours
- • Earlier = better outcomes
- • Don't delay for level results
Acetaminophen Poisoning Stages
0-24 hours
Nausea, vomiting, malaise
24-72 hours
RUQ pain, elevated LFTs
72-96 hours
Fulminant hepatic failure
4-14 days
Recovery or transplant
High-Risk Groups
- • Chronic alcohol use
- • Malnutrition
- • Chronic liver disease
- • Enzyme-inducing drugs
- • Fasting state
- • Infants and elderly
- • Genetic CYP2E1 variants
Understanding Acetaminophen Toxicity and NAC Treatment
Mechanism of Toxicity
In therapeutic doses, 95% of acetaminophen is safely metabolized through conjugation. The remaining 5% is oxidized to NAPQI (N-acetyl-p-benzoquinoneimine), a toxic metabolite that is normally neutralized by glutathione.
In Overdose
- •More drug follows oxidation pathway → more NAPQI
- •Glutathione stores become depleted
- •NAPQI accumulates causing hepatocellular necrosis
- •Progressive liver failure can result in death
How NAC Works
N-acetylcysteine (NAC) is the specific antidote for acetaminophen poisoning:
- •Provides glutathione precursors
- •Promotes conjugation pathway
- •Neutralizes toxic NAPQI
- •Prevents hepatocellular damage
Key Point: NAC is virtually 100% effective in preventing liver damage if started within 8 hours of ingestion.
Rumack-Matthew Nomogram
The Rumack-Matthew nomogram is used to determine the need for NAC treatment based on serum acetaminophen levels and time since ingestion. It has two important lines:
Toxic Line
200 mcg/mL at 4 hours, declining to 6.25 mcg/mL at 24 hours. Levels above this line predict hepatotoxicity.
Treatment Line
150 mcg/mL at 4 hours (75% of toxic line). NAC treatment is recommended for levels above this line.
⚠️ CRITICAL MEDICAL EMERGENCY DISCLAIMER
THIS IS A LIFE-THREATENING MEDICAL EMERGENCY. Acetaminophen overdose can cause fulminant hepatic failure and death. Time is critical - hepatotoxicity risk increases rapidly with delayed treatment.
IMMEDIATE ACTION REQUIRED: Call Poison Control (1-800-222-1222) or Emergency Services (911) immediately. This calculator is for healthcare professionals only and should never replace emergency medical care or poison control consultation.
Healthcare providers must verify all calculations independently and consider individual patient factors. NAC dosing errors can be harmful. Always follow institutional protocols and current poison control recommendations.
DO NOT DELAY TREATMENT waiting for calculator results or serum levels. Early NAC administration saves lives.