Like aspirin, paracetamol poisoning involves metabolism of the drug, rather than the usual pharmacodynamics effect of the drug (pain and fever relief) in massive excess. Paracetamol metabolism by the body requires endogenous glutathione, which is rapidly depleted in paracetamol poisoning, leading to production of alternative, toxic metabolites, fulminant liver failure and death. Patients with high serum levels of paracetamol can be treated with the glutathione precursor acetylcysteine. Unlike aspirin intoxication, patients may have few symptoms during the first 24 hours of poisoning.
paracetamol acetaminophen poisoning nomogram
Figure 1: Typically, patients require acetylcysteine treatment if their blood paracetamol levels are above the normal treatment line. Otherwise, observation is probably all that is required. Patients who may have elevated liver enzymes (drugs such as phenytoin, phenobarbitone, carabamazepine and rifampicin), are HIV positive, have liver disease or are chronic alcohol abusers should be treated if their paracetamol levels are above the high-risk line.

Oral activated charcoal can be used to limit absorption if paracetamol ingestion is recent (within 4 hours). Blood paracetamol levels are more reliable if taken 4-16 hours after ingestion.

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