Toxic concentration

The pharmacokinetics of modified-release paracetamol after deliberate self-poisoning have not been well defined. Observational studies show slow absorption and a delayed peak serum paracetamol concentration.

Do not use the paracetamol toxicity treatment nomogram to decide whether to treat patients who have ingested 10 g (or 200 mg/kg in a patient under 50 kg) or more of modified-release paracetamol—start acetylcysteine immediately in these patients. In this scenario, the serum paracetamol concentration is used to choose the appropriate acetylcysteine regimen.

Note: The nomogram is not used to decide whether to start acetylcysteine therapy when the patient has ingested 10 g (or 200 mg/kg in a patient under 50 kg) or more of modified-release paracetamol.

In patients who have ingested less than 10 g (or 200 mg/kg in a patient under 50 kg) of modified-release paracetamol, use the treatment nomogram 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.

Note: Check the serum paracetamol concentration units reported by the laboratory before using the nomogram.

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.