138 - Acetaminophen

Abstract

Acetaminophen toxicity is a leading cause of overdose, drug-induced liver injury, liver transplant, and fatality in the United States. Since clinical signs of toxicity are delayed, it is crucial to check an acetaminophen serum concentration in all patients who report an ingestion. Toxicity includes vomiting, right upper quadrant abdominal pain, elevated transaminases, and can progress to fulminant hepatic failure including acidosis, encephalopathy, coagulopathy, and cerebral edema. Intentional ingestions as well as repeated supratherapeutic dosing can result in hepatotoxicity. In a patient with an intentional ingestion with a known time frame, the acetaminophen concentration on the nomogram at 4 hours or more post-ingestion is used to determine whether N-acetylcysteine (NAC) therapy is indicated. NAC is very effective at preventing hepatotoxicity if given with 8 hours after ingestion. The decision to start NAC in patients with repeated supratherapeutic use or those who have already developed hepatotoxicity should not be based on the nomogram. Late or prolonged administration of NAC is beneficial even with low or absent acetaminophen concentrations if hepatotoxicity is evident. NAC is safe in pregnancy. The King’s College Criteria are useful to predict who will develop fulminant hepatic failure and include pH <7.3, Cr >3.3, INR >5, and grade III or worse encephalopathy.