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    Acetaminophen Overdose and NAC Dosing

    Calculates PO/IV NAC dosing for acetaminophen overdose (and nomogram to determine toxic 4 hour level).
    When to Use
    Why Use

    When to use the Rumack-Matthew nomogram:

    • Acute, single ingestions (where entire ingestion occurs within an 8-hour period).
    • A known time of ingestion.
    • Immediate release formulation.
    • Absence of formulations or coingestants that alter absorption and bowel motility (e.g. anticholinergics, opioids).
    • An acetaminophen concentration obtained prior to 4 hours post-ingestion cannot be plotted on the Rumack-Matthew nomogram, and only confirms acetaminophen exposure, not toxicity.
    • Get an accurate time of ingestion: the Rumack-Matthew nomogram is entirely dependent on knowing time of ingestion.
    • Start NAC treatment within 8 hours post-ingestion to decrease the risk of hepatotoxicity (AST or ALT > 1000 IU/L).
    • In patients presenting 8-24 hours post-ingestion, start NAC while awaiting the acetaminophen concentration; once this is resulted, NAC can be continued or discontinued depending on the level.
    • The Rumack-Matthew nomogram is the most sensitive risk prediction tool in medical toxicology.
    • It identifies patients at very low risk of developing hepatotoxicity after acetaminophen overdose and who do not require NAC.
    • All patients above the nomogram line should be treated with NAC to decrease the risk of developing hepatotoxicity (See Evidence).
    Rumack-Matthew Nomogram


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    Creator Insights
    Dr. Barry H. Rumack

    About the Creator

    Barry H. Rumack, MD, is currently director emeritus of the Rocky Mountain Poison and Drug Center and director, Office of Professionalism at UC Denver. He is a retired professor emeritus of pediatrics at the University of Colorado School of Medicine.

    To view Dr. Barry H. Rumack's publications, visit PubMed

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    MDCalc loves calculator creators – researchers who, through intelligent and often complex methods, discover tools that describe scientific facts that can then be applied in practice. These are real scientific discoveries about the nature of the human body, which can be invaluable to physicians taking care of patients.
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