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Acetaminophen is the most important overdose in toxicology

Step 1: Check a Serum Acetaminophen Level

  • Common situations where testing is ordered
    • Suicidal ideation
    • Severe depression
    • Overdose

Step 2: Consult the Rumack-Matthew nomogram

  • Only works for acute/single ingestions of acetaminophen
  • Loses reliability if patient is on drugs that affect bowel motility
  • If the time of ingestion is KNOWN
    • Measure acetaminophen level 4 hours post-ingestion
    • Plot on nomogram and treat if above line
  • If time of ingestion is UNKNOWN
    • Determine earliest possible time of ingestion
    • Plot on nomogram and treat if above line

Step 3: Order hepatic labs (LFTs)

  • AST
  • ALT
  • Alk Phos
  • PTT/PT/INR

Step 4: Identify Phase of Toxicity

  • Phase 1/Day 1
    • High acetaminophen levels
    • Normal LFTs
    • Minimal symptoms
  • Phase 2/Day 2
    • Acetaminophen level starts decreasing
    • LFTs level starts increasing
    • Mild GI symptoms develop
      • Abdominal pain
      • Nausea/vomiting
  • Phase 3/Day 3
    • Acetaminophen levels are normalized
    • LFTs are peaking
  • Phase 4
    • Recovery

Step 5: Give N-Acetylcysteine (NAC)

  • If patient meets criteria on Rumack-Matthew nomogram
  • If patient is in phase 1, 2, or 3

Additional Reading

  • Acetaminophen Overdose and NAC Dosing (MDCalc)