Overview Paracetamol overdose is a common cause of hospital presentation. Paracetamol is a analgesic and antipyretic drug used in both children and adults. Its mechanism of action is yet to be fully determined, and is likely to involve a number of pain pathways.
When taken in excess it can cause signs such as vomiting, right upper quadrant pain and altered mental status. The most serious outcome of paracetamol overdose is acute hepatic failure which could lead to death. Although hepatic injury and death is rare it is important to identify patients at risk, measure paracetamol levels using a normogram and treat accordingly. High paracetamol levels is treated with N-acetylcysteine.
Mechanism of action (not fully understood) several theories:
Absorption
Metabolism Paracetamol is metabolised in the liver.
Think When an overdose occurs, the normal metabolic pathways become saturated and more paracetamol is shunted through the P450 system increasing NAPQI levels. NAPQI is toxic |
The clinical features of paracetamol toxicity is divided into 4 stages based on the time after ingestion
Stage One - first 24 hours
Stage Two 24-48hours
Stage Three 48-72 hours
Stage Four 72hours+
acute tubular necrosis, and interstitial nephritis, but these are usually observed after either acute overdose
Metabolism Paracetamol is metabolised in the liver.
However, when an overdose occurs, the normal metabolic pathways become saturated and more paracetamol is shunted through the P450 system increasing NAPQI levels.
Important questions to ask in history
Acute single overdose (adult)