Acetaminophen-Link To And Excerpts From The IBCC Chapter On Analgesia

In this post I link to and excerpt the Acetaminophen section of Analgesia for the critically ill patient, August 9, 2020 by Dr Josh Farkas, author of the Internet Book Of Critical Care [Link is to the Table of Contents].

Note to myself: Review the IBCC chapter, Acetaminophen toxicity.
December 22, 2016 by Dr Josh Farkas

Here are the two resources on liver disease that are relevant to acetaminophen toxicity:


general comments & mechanism of action
  • Acetaminophen is a mild-moderately effective analgesic with an excellent safety profile.  It forms the first level of the analgesic ladder due to its safety, rather than its efficacy.  Acetaminophen is often overlooked because it isn’t very potent.  However, scheduled acetaminophen may nonetheless play a useful role in multi-modal analgesia.  RCTs and meta-analyses demonstrate that acetaminophen is an effective analgesic in a variety of contexts, with benefits which may include reduced opioid requirements, avoidance of delirium, and avoidance of nausea/vomiting. (20189753307265453030512430778597)
  • Acetaminophen is a centrally acting, noncompetitive reversible inhibitor of cyclooxygenase (COX) enzymes, with analgesic and antipyretic effects. (30845871)
  • The usual dose is 650-1,000 mg q6hr.  For patients with ongoing pain this should be scheduled, to provide a baseline level of analgesia.
  • Acetaminophen may be given PO, PR, or IV.  PO is preferred, because IV is expensive (although this varies in different countries).
  • Available RCTs have found no difference in efficacy between IV versus oral route.
  • 📚  Medscape monograph on acetaminophen
contraindications & complications
  • In severe alcoholism, stable cirrhosis, or low body weight (<50 kg), the dose should be reduced to 2 grams per day (at most).(25477978)
  • In acute liver injury* or decompensated cirrhosis**, acetaminophen should be entirely avoided.
  • In neutropenia, acetaminophen might be avoided, to allow for early detection of neutropenic fever.

*Please see Acute Liver Failure – LiverTox – NCBI Bookshelf, Dec 11, 2019

**For an explanation of the diagnosis of compensated cirrhosis versus decompensated cirrhosis, please see Stages of Cirrhosis from Viral Hepatitis and Liver Disease from the U.S. Department of Veterans Affairs. Accessed 2-23-2021.

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