Paracetamol toxicity

Paracetamol toxicity
Paracetamol
Classification and external resources
Specialty	Toxicology
ICD-10	T39.1
ICD-9-CM	965.4
MedlinePlus	002598
eMedicine	ped/7
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Paracetamol toxicity is caused by excessive use or overdose of the medication paracetamol (acetaminophen). Most people with paracetamol toxicity have no symptoms in the first 24 hours following overdose. Others may initially have nonspecific complaints such as vague abdominal pain and nausea. With time, signs of liver injury may develop; these include low blood sugar, low blood pH, a tendency to bleed easily, and hepatic encephalopathy. Some will spontaneously resolve, although untreated cases may result in death. In the United States and the United Kingdom it is the most common cause of acute liver failure. Paracetamol toxicity is one of the most common causes of poisoning worldwide.

Drug-induced liver damage (hepatotoxicity) results not from paracetamol itself, but from one of its metabolites, N-acetyl-p-benzoquinoneimine (NAPQI). NAPQI decreases the liver's natural antioxidant glutathione and directly damages cells in the liver, leading to liver failure. Risk factors for toxicity include alcohol abuse, fasting, anorexia nervosa, and drug interactions with medications such as isoniazid.

Treatment is aimed at removing the paracetamol from the body and restoring glutathione. Activated charcoal can be used to decrease absorption of paracetamol if the person presents for treatment soon after the overdose; the antidote acetylcysteine acts as a precursor for glutathione, helping the body regenerate enough to prevent damage to the liver. N-acetylcysteine can neutralize NAPQI by itself as well. A liver transplant is often required if damage to the liver becomes severe. Patients treated early have a good prognosis, whereas patients that develop major liver abnormalities typically have a poor outcome.

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