Template:Adult NAC dosing


  • Less preferred than IV route due to unpleasant taste and smell
  • 140 mg/kg PO load
  • 70 mg/kg PO q4hr x17 doses additional; dilute to 5% soln


  • Loading dose: 150mg/kg in 100 mL D5W over 60min
  • Second (maintenance) dose: 50mg/kg in 250 mL D5W over 4hr
  • Third dose: 100mg/kg in 500 mL D5W over 16hr


  • Almost 100% effective if given <8 hr post-ingestion; less effective if 16-24 hr post-ingestion
  • May still be useful >24 hr post-ingestion, even with fulminant hepatic failure. Give NAC until LFTs improve (not until APAP level is 0) [1] [2]
  • Be aware NAC treatment may affect PT. May see a dose-dependent increase in PT following NAC in patients without hepatotoxicity. [3]
  • Keays R, Harrison PM, Wendon JA, et al. Intravenous acetylcysteine in paracetamol-induced fulminant hepatic failure: a prospective controlled trial. BMJ. 1991;303(6809):1026-1029. (Prospective randomized controlled trial; 50 patients)
  • Harrison PM, Keays R, Bray GP, et al. Improved outcome of paracetamol-induced fulminant hepatic failure by late administration of N-acetylcysteine. Lancet. 1990;335(8705):1572- 1573. (Retrospective analysis; 100 patients)
  • Wasserman GS, Garg U. Intravenous administration of Nacetylcysteine: interference with coagulopathy testing. Ann Emerg Med. 2004;44(5):546-547. (Letter)