N-Acetylcysteine (NAC)

Liverpool Hospital Emergency Department


Paracetamol overdose that may be associated with liver injury  

Acute Single ingestion (Immediate Release) 

  • > 10g or > 200mg/kg (whichever is less) 
  • Delayed presentation of overdose (>8 hours or delay in paracetamol level result)
  • Paracetamol level above the treatment nomogram
  • Acute Single Ingestion (Modified Release)
  • > 10g or > 200mg/kg (whichever is less)
  • Delayed presentation of overdose (>4 hours or delay in paracetamol  level result) 

Two paracetamol levels must be reviewed in line with MJA  guidelines 

  • Repeated supratherapeutic ingestion (nomogram is not used)
  • > 10g or 200mg/kg per 24hrs
  • >12g or 300mg/kg per in 48hrs 
  • Greater than daily therapeutic dose with GI symptoms 


  • 200mg/ml injectable (2g/10ml ampoule) 

Dosage and Administration 

2 bag protocol (see next page) 

  • 200mg/kg over 4hrs in total volume 500ml 0.9% saline or 5% glucose
  • 100mg/kg over 16hrs in total volume 1L 0.9% saline or 5% glucose 

May require another 16-hour bag in line with guidelines 

Side Effects 

Anaphylactoid reactions – (up to 50%) ->warn patients about this (less with new  protocol) 

  • Hypotension/ flushing/ angioedema/ rash 
  • Treat with loratadine 10mg 
  • If severe – cease and restart when reaction settled 

Pit Falls 

  • Paediatrics – same dose (mg/kg) but reduce volume of fluid –(7ml/kg)
  • Errors in conversion of mg to mls please refer to policy guideline
  • Incorrect use of paracetamol lab concentration levels on nomogram
  • Pregnancy – Safe for use 

MUST START within 8hrs of overdose (4 hours if MR) or ASAP if overdose >200mg/kg  or presents  

In large ingestions consider double dose NAC (2nd bag) in discussion with poisons  network  

Follow MJA guidelines regarding cessation