Paracetamol Overdose

Paracetamol Overdose

Written by Dr Andrew Lam

Clinical Stages of Paracetamol Overdose

Stage I (0-24 hours) – relatively non-specific with nausea, vomiting, malaise and diaphoresis, though some patients may be asymptomatic. Uncommonly may have CNS depression

Stage II (24-72 hours) –  resolution of initial Stage I symptoms with subsequent development of RUQ pain and hepatic enlargement. Uptrending LFT’s. 

Stage III (72-96 hours) –  Peak LFT derangement with manifestations of liver failure (jaundice, hepatic encephalopathy, coagulopathy). Most people who die from their overdose will die in this stage from multi-organ failure 

Stage IV (Days 4-7) – Symptoms resolve and patients recover, usually by day 7. Those who have had large overdoses or who were severely ill may have more protracted recoveries past a week

Paracetamol Overdose Normogram

• Take serum paracetamol level at least 4 hours post-ingestion (earlier levels will be inaccurate)
• If the level lies above the line on the normogram, commence NAC infusion
• If the level is greater than double the line on the normogram, commence a high dose NAC infusion instead
• An extended NAC infusion should be commenced if ALT > 50 or paracetamol level >10 on repeat bloods, 2 hours prior to cessation of original NAC infusion
• NAC infusion can then cease when paracetamol level < 10, ALT is downtrending and INR <2. 

N.B. If the patient has ingested a toxic dose of paracetamol (>10g) and presents >8 hours post-ingestion, commence NAC infusion before paracetamol level returns.

NAC Regimens

Standard NAC Infusion: 

200mg/kg of NAC in 500ml’s over 4 hours, and then the 2nd bag with 100mg/kg in 1L over 16 hours

Higher Dose NAC Infusion:

200mg/kg of NAC in 500ml’s over 4 hours, and the 2nd bag contains 200mg/kg in 1L over 16 hours

Extended NAC Infusion

100mg/kg of NAC in 1L over 16 hours