This occurs via conjugation with the addition of glucuronide to form a water soluble metabolite that can be excreted in the urine.

Paracetamol is primarily metabolised in the liver. This may be significantly increased in the presence of hepatic dysfunction. Once ingested, paracetamol reaches peak concentration at 4 hours with an average half life of 2 hours. Paracetamol is primarily metabolised in the liver to non-toxic metabolites, in overdose these pathways become overwhelmed. If there is uncertainty whether the presentation is unintentional therapeutic excess, patients should be managed as a staggered overdose. Patients may have inadvertently taken paracetamol in addition to a paracetamol containing product (e.g. Patients should have ingested paracetamol at a dose greater than the licensed daily dose (4g/24 hours) and ≥75 mg/kg over 24 hours. pain, fever) without intention of self-harm. This refers to the unintentional use of excess paracetamol with the intent to treat an underlying problem (e.g. If a significant delay is suspected, treatment is usually initiated first whilst awaiting further investigations. This may be in the context of an acute overdose or staggered overdose. This refers to a delay between the time of overdose and presentation to medical care. If the time of ingestion is unknown patients should be treated as a ‘staggered overdose’. However, if paracetamol above the recommended daily dose (4g/24 hours in adults) is ingested for the two preceding days or more, the risk increases.Īll patients that have taken a staggered overdose should be referred to hospital for assessment.

Doses consistently < 75 mg/kg in any 24 hour period are unlikely to be toxic. Rarely, toxicity may occur for ingestions between 75-150 mg/kg. Serious toxicity may occur in patients who have ingested > 150 mg/kg in any 24 hour period. This refers to excessive ingestion of paracetamol over a period longer than one hour, usually in the context of self-harm. Serious toxicity is unlikely if a patient has ingested 75 mg/kg, are symptomatic, or need urgent psychiatric assessment (if taken in context of self-harm), hospital admission is warranted. This refers to the ingestion of a potentially toxic dose of paracetamol within one hour or less. It is essential to understand and characterise the type of paracetamol ingestion as it determines management.

Antidote to paracetamol overdose