Paucis Verbis: Acetaminophen toxicity

Paucis Verbis: Acetaminophen toxicity


acetaminophen toxicityDid you know that the American Association of Poison Control Centers reports that 10% of poison center calls are related to acetaminophen ingestions? That’s a lot. This Paucis Verbis card reviews the basics of acetaminophen toxicity. I included the Rumack Matthew nomogram to help you plot out the patient’s risk for hepatotoxicity.

In the Emergency Department, we often screen for acetaminophen toxicity for patients who may have ingested substances as a suicide attempt. We check the serum acetaminophen level 4 hours post-ingestion. Occasionally, we are surprised by a toxic level because in the first 24 hours, because symptoms are can be mild and nonspecific (abdominal pain, nausea, lethargy).

Rule of 150

  • The toxic ingestion dose of acetaminophen is 150 mg/kg.
  • The serum acetaminophen level when N-acetylcysteine treatment should be started is 150 mcg/mL (see Rumack Matthew nomogram)
  • The starting IV dose of N-acetylcysteine is 150 mg/kg over 15 minutes.

Adapted from 1
Go to the ALiEM Cards site for more resources.

Larson A. Acetaminophen hepatotoxicity. Clin Liver Dis. 2007;11(3):525-48, vi. [PubMed]

Michelle Lin, MD
ALiEM Editor-in-Chief
Academy Endowed Chair of EM Education
Professor of Clinical Emergency Medicine
University of California, San Francisco
Michelle Lin, MD
Michelle Lin, MD

Latest posts by Michelle Lin, MD (see all)

  • SFTox

    Hi Michelle. No poison center or toxicologist uses oral N-Ac for 72 hrs anymore. 20 hours needed only

  • Hey @SFTox: Thanks for catching this. This is a good review article, but it’s from 2007. Agreed that for uncomplicated overdoses, only 20 hours is needed. Will need more doses if levels still rising though. So I changed the wording to say “may need as many as 17 doses”. Good catch!

  • SFTox

    The Tox curmudgeon says that at the end of the initial N-Ac tx by oral or IV N-Ac, if AST/ALT are rising or [apap] is still detectable, N-Ac must continue indefinitely, by either route… I would leave out the “17 doses” altogether.

  • Michelle:

    Most toxicologists would recommend giving the first dose of IV N-Ac (150 mg/kg) over one hour (rather than 15 minutes) to minimize the chance of an anaphylactoid reaction. In fact, this is now the official recommendation.

  • Good call @SFTox and Leon. One of the down sides of summarizing a review article from 2007 is outdated info. Thanks guys. Will change the card.