USMLE Prep - Medical Reference Library

Acetaminophen (Paracetamol) Overdose — ED Management

System: Toxicology • Reviewed: Aug 31, 2025 • Step 1Step 2Step 3

Synopsis:

Obtain level at ≥4 hours post ingestion; use Rumack-Matthew nomogram; start N-acetylcysteine when indicated or if timing uncertain with elevated level; give activated charcoal within 4 hours in appropriate patients.

Key Points

  • Stabilize ABCs; begin targeted evaluation without delaying life-saving therapy.
  • Use system-specific risk tools to guide testing and disposition.
  • Order high-yield tests first; escalate imaging when indicated.
  • Start evidence-based initial therapy and reassess frequently.

Algorithm

  1. Primary survey and vitals; IV access and monitors.
  2. Focused history/physical; identify red flags and likely etiologies.
  3. Order system-appropriate labs and imaging (see Investigations).
  4. Initiate guideline-based empiric therapy (see Pharmacology).
  5. Reassess response; arrange consultation and definitive management.

Clinical Synopsis & Reasoning

For Acetaminophen Overdose Ed, frame the differential by acuity and pathophysiology, then align diagnostics to the leading hypotheses. Prioritize stabilization while obtaining high‑yield studies such as CBC (Baseline hematology), BMP (Electrolytes/renal). Incorporate bedside imaging and targeted labs to define severity and identify complications; synthesize results with clinical trajectory to refine the working diagnosis and disposition needs.


Treatment Strategy & Disposition

Initiate disease‑directed therapy alongside supportive care, titrating to objective response. Pharmacologic options commonly include Analgesia/Antipyretics. Use validated frameworks (e.g., N-acetylcysteine Regimens (Abbrev.)) to guide escalation and site of care. Address precipitating factors, de‑escalate empiric therapies with data, and arrange follow‑up for monitoring and risk‑factor modification; admit patients with instability, high risk of deterioration, or needs for close monitoring.


Epidemiology / Risk Factors

  • Risk factors vary by condition and patient profile

Investigations

TestRole / RationaleTypical FindingsNotes
CBCBaseline hematologyAbnormal counts
BMPElectrolytes/renalDerangements

N-acetylcysteine Regimens (Abbrev.)

RouteTypical protocol
IV3-bag or 2-bag weight-based protocols over ~20–24 h
Oral140 mg/kg load then 70 mg/kg q4h ×17 doses

Pharmacology

MedicationMechanismOnsetRole in TherapyLimitations
N-acetylcysteineGlutathione precursorHoursHepatoprotection per nomogramAnaphylactoid reaction (IV); ED use

Prognosis / Complications

  • Prognosis depends on severity, comorbidities, and timeliness of care

Patient Education / Counseling

  • Explain red flags and when to seek emergent care.
  • Reinforce medication adherence and follow-up plan.

Notes

Chronic or staggered overdoses may require treatment even with lower levels; use clinical judgment. Consider extended-release products and co-ingestants that delay absorption.


References

  1. AACT/ACMT Acetaminophen Position Statements — Link
  2. ACEP Toxicology Section — Link