What is the approach to assessing a patient with acetaminophen (paracetamol) overdose?

From the Guidelines

Assessing a patient with acetaminophen overdose requires immediate attention and a thorough approach. First, determine the time and amount of acetaminophen ingested. If the overdose is suspected to have occurred within 8-10 hours, administer activated charcoal to help absorb the toxin, but only if the patient is awake and able to protect their airway 1.

Next Steps

• Calculate the acetaminophen dose ingested and plot it on the Rumack-Matthew nomogram to determine the need for antidote treatment 1.
• If the dose is toxic, administer N-acetylcysteine (NAC) as an antidote, with a loading dose of 150 mg/kg over 1 hour, followed by 50 mg/kg over 4 hours, and then 100 mg/kg over 16 hours 1.
• Monitor liver function tests, including AST, ALT, and bilirubin, as well as prothrombin time and INR 1.
• Assess for any signs of liver failure, such as coagulopathy, encephalopathy, or hypoglycemia 1.
• In severe cases, consider transferring the patient to a liver transplant center 1.

Special Considerations

• For patients with repeated supratherapeutic ingestions, treatment with NAC is recommended for serum acetaminophen concentrations of greater than or equal to 10 mg/mL or greater than normal aminotransferase concentrations (AST or ALT > 50 IU/L) 1.
• For patients with extended-release preparations of acetaminophen, the decision to treat must be individualized due to limited systematic data 1.

From the FDA Drug Label

ACETAMINOPHEN ASSAYS - INTERPRETATION AND METHODOLOGY The acute ingestion of acetaminophen in quantities of 150 mg/kg or greater may result in hepatic toxicity. However, the reported history of the quantity of a drug ingested as an overdose is often inaccurate and is not a reliable guide to therapy of the overdose THEREFORE, PLASMA OR SERUM ACETAMINOPHEN CONCENTRATIONS, DETERMINED AS EARLY AS POSSIBLE, BUT NO SOONER THAN 4 HOURS FOLLOWING AN ACUTE OVERDOSE, ARE ESSENTIAL IN ASSESSING THE POTENTIAL RISK OF HEPATOTOXICITY. IF AN ASSAY FOR ACETAMINOPHEN CANNOT BE OBTAINED, IT IS NECESSARY TO ASSUME THAT THE OVERDOSE IS POTENTIALLY TOXIC.

The approach to assessing a patient with acetaminophen (paracetamol) overdose involves:

• Determining plasma or serum acetaminophen concentrations as early as possible, but no sooner than 4 hours following an acute overdose
• Using a nomogram to determine if the plasma concentration is in the potentially toxic range
• Not waiting for assay results to begin acetylcysteine treatment if the overdose is suspected to be potentially toxic 2
• Considering the overdose potentially toxic if an assay for acetaminophen cannot be obtained 2

From the Research

Approach to Assessing a Patient with Acetaminophen Overdose

The approach to assessing a patient with acetaminophen overdose involves several key steps:

• Patients who present early should be offered activated charcoal to reduce absorption 3, 4, 5
• The acetaminophen nomogram is used to assess the need for treatment in acute immediate-release overdoses with a known time of ingestion 3, 6
• Patients at risk of acute liver injury should receive acetylcysteine 3, 4, 7, 5, 6
• Scenarios that require different management pathways include modified-release, large/massive, and repeated supratherapeutic ingestions 3

Treatment Options

Treatment options for acetaminophen overdose include:

• Activated charcoal to reduce absorption 4, 5
• N-acetylcysteine as an antidote 4, 7, 5, 6
• Liver transplantation in cases of fulminant hepatic failure 4, 5
• Gastric lavage and ipecacuanha may also be used to reduce absorption, but their clinical benefit is unclear 4, 5

Important Considerations

Important considerations in the management of acetaminophen overdose include:

• Early recognition and prompt treatment are crucial to prevent hepatic injury 6
• The selection criteria for N-acetylcysteine treatment and liver transplantation are not clear 4, 5
• The Rumack-Matthew nomogram is a useful tool to assess risk and guide management in acute overdose 6
• Standard courses of N-acetylcysteine may need to be extended in patients with persistently elevated plasma concentrations of acetaminophen or with signs of hepatic injury 6