Shorter duration of oral N-acetylcysteine therapy for acute acetaminophen overdose

Ann Emerg Med. 2000 Apr;35(4):363-8.


Study objective: We sought to evaluate the safety and efficacy of a shorter N-acetylcysteine (NAC) regimen in the treatment of acute acetaminophen overdose.

Methods: We performed a retrospective case series in a large urban county hospital. Of 305 patients identified through the emergency department, 75 patients met the criteria inclusion: an acute overdose ingestion, serum acetaminophen concentration in toxic range according to the Rumack-Matthew nomogram, and oral NAC treatment initiated within 24 hours of the ingestion. The regional poison control center recommended oral treatment with NAC 140 mg/kg, followed by maintenance doses of 70 mg/kg every 4 hours until the serum acetaminophen level was no longer detectable, rather than the standard 72-hour treatment regimen.

Results: The primary outcome measure was the development of hepatotoxicity. Twenty-five (33.3%) patients were treated for a period of less than 24 hours, 25 (33.3%) were treated for 24 to 36 hours, and 25 (33.3%) were treated for 37 to 64 hours; the mean and median duration of treatment was 31 hours. None of the patients treated for less than 24 hours had evidence of hepatotoxicity (aspartate aminotransferase [AST] or alanine aminotransferase [ALT] level >1,000 IU/L); hepatotoxicity developed in 2 (8%) patients treated for 24 to 36 hours and 4 (16%) patients treated for 37 to 64 hours. There were no deaths or patients who received liver transplantation. The overall incidence of hepatotoxicity in our patients was similar to that found in other protocols with administration of oral NAC for 72 hours or intravenous NAC for 20 or 48 hours.

Conclusion: This observational study suggests that a shorter course of oral NAC therapy in patients who do not show evidence of hepatotoxicity within 36 hours of an acute acetaminophen overdose is safe and effective.

MeSH terms

  • Acetaminophen / blood
  • Acetaminophen / poisoning*
  • Acetylcysteine / administration & dosage
  • Acetylcysteine / therapeutic use*
  • Administration, Oral
  • Adolescent
  • Adult
  • Age Distribution
  • Aged
  • Analgesics, Non-Narcotic / blood
  • Analgesics, Non-Narcotic / poisoning*
  • Child
  • Drug Overdose / drug therapy
  • Emergency Service, Hospital
  • Female
  • Free Radical Scavengers / administration & dosage
  • Free Radical Scavengers / therapeutic use*
  • Hospitals, Urban
  • Humans
  • Liver / drug effects
  • Liver / enzymology
  • Male
  • Middle Aged
  • Retrospective Studies
  • Sex Distribution
  • Time Factors


  • Analgesics, Non-Narcotic
  • Free Radical Scavengers
  • Acetaminophen
  • Acetylcysteine