Acetaminophen (Paracetamol)

00:00 / 00:00



Acetaminophen (Paracetamol)

Prerequisite basic sciences

Prerequisite basic sciences

Prerequisite basic sciences

Prerequisite basic sciences

Prerequisite basic sciences


Acetaminophen (Paracetamol)


0 / 14 complete


Acetaminophen (Paracetamol)

of complete

Memory Anchors and Partner Content

External References

First Aid








Acetaminophen p. 498

vs aspirin for pediatric patients p. 498

free radical injury and p. 213

hepatic necrosis from p. 250

for osteoarthritis p. 476

tension headaches p. 536

toxicity effects p. 498

toxicity treatment for p. 249

Glutathione p. 81

acetaminophen and p. 498

External Links


Acetaminophen, also known as paracetamol, is mainly used to treat pain and fever. These conditions are related to an increased production of pro-inflammatory chemicals called prostaglandins.

Now, acetaminophen works by decreasing the production of prostaglandins, thereby relieving pain, and reducing fever.

In order to understand how acetaminophen works, first we need to talk briefly about inflammation, which is the body’s response to a harmful stimulus, such as infection or injury.

So, during inflammation, your immune cells use an enzyme called phospholipase A2 to take membrane phospholipids and make a 20 carbon polyunsaturated fatty acid, called arachidonic acid.

Arachidonic acid is a substrate for an enzyme called cyclooxygenase or COX.

The enzyme cyclooxygenase exists in two different isoforms: COX-1 and COX-2.

COX-1 is a constitutive enzyme, meaning that it’s always active, while on the other hand, COX-2 is an inducible enzyme, meaning that it must be turned on to function. This is usually triggered by immune cells and vascular endothelial cells during inflammation.

Both enzymes produce prostaglandin E2 (PGE2) and prostacyclin (PGI2), which cause vasodilation and attract different immune cells to the area.

They also act on neurons that detect pain, called nociceptors, and make them more sensitive to stimuli by lowering their threshold for activation.

Finally, they stimulate the hypothalamus to increase the body temperature, causing fever.

Prostaglandin E2 also has other effects like causing uterine contractions, decreasing the secretion of acid, and increasing the production of protective mucus in the stomach.

Alright, now let’s focus on acetaminophen. Acetaminophen is administered orally, rectally, or intravenously; and it works by reversibly inhibiting COX in the central nervous system, thereby decreasing production of the prostaglandins that cause fever and pain.


Acetaminophen (Paracetamol) is a medication used to relieve pain and reduce fever. It is usually taken orally, but can also be given intravenously. Acetaminophen is one of the most common medications used and is generally considered safe when taken as directed. However, acetaminophen can cause serious liver damage if too much is taken or if it is taken with certain other medications such as pexidartinib.


  1. "Katzung & Trevor's Pharmacology Examination and Board Review,12th Edition" McGraw-Hill Education / Medical (2018)
  2. "Rang and Dale's Pharmacology" Elsevier (2019)
  3. "Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th Edition" McGraw-Hill Education / Medical (2017)
  4. "Kinetics and metabolism of paracetamol and phenacetin." British Journal of Clinical Pharmacology (1980)
  5. "Acetaminophen poisoning and toxicity" Pediatrics (1975)
  6. "Acetaminophen Toxicity" New England Journal of Medicine (1988)
  7. "What is the most appropriate dose of N-acetylcysteine after massive acetaminophen overdose?" Clin Toxicol (Phila) (2019)

Copyright © 2023 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Cookies are used by this site.

USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.