Toxic concentration

The paracetamol toxicity treatment nomogram (Paracetamol toxicity treatment nomogram) is used to decide whether to start acetylcysteine therapy. The serum paracetamol concentration is plotted versus time since ingestion on the nomogram—acute liver injury can occur when the serum paracetamol concentration is on or above the treatment nomogram line. The serum paracetamol concentration can be reported as mg/L (left axis) or micromol/L (right axis). Check the units reported by the laboratory before using the nomogram.

If a patient has taken multiple staggered doses of paracetamol, use the time of the first dose to determine the time since ingestion.

Patients with an initial serum paracetamol concentration double or higher than the treatment nomogram line versus the time since ingestion are at greater risk of acute liver injury and need a high-dose acetylcysteine regimen.