paracetamol

Last edited 11/2023 and last reviewed 11/2023

Paracetamol is one of the most popular over-the-counter analgesic preparations, used regularly by millions of people throughout the world. It is also an ingredient of other brand name analgesic preparations, for example calpol, anadin extra and lemsip.

  • has a unique clinical pharmacological profile that includes potent analgesic and antipyretic effects and no or little anti-inflammatory activity as well as minor gastrointestinal, renal, and vascular side effects (1)

  • typical licensed indications for paracetamol in adults include treatment of most painful and febrile conditions, including headache, neuralgia, sore throat, and rheumatic pain (2)

  • acetaminophen (paracetamol; N-acetyl-p-aminophenol) is the active metabolite of phenacetin
    • unlike phenacetin, paracetamol is not carcinogenic (1)

  • oral paracetamol has excellent bioavailability with peak plasma concentrations occurring within 30-60 min after ingestion
    • plasma t1/2 is about 120 min

  • binds to plasma proteins less than NSAIDs and diffuses throughout most body fluids.

Potential risk factors for hepatotoxicity with paracetamol include (2):

  • dry body weight under 50 kg
  • use of paracetamol in older or frail patients
  • cachexia
  • renal insufficiency
  • chronic malnutrition
  • chronic dehydration
  • decompensated liver disease
  • chronic alcohol consumption or regular consumption of alcohol in excess of recommended amounts
  • long term treatment with liver enzyme inducing drugs, such as
    • carbamazepine, phenytoin, primidone, rifampicin, phenobarbital, St John's Wort, or other drugs that induce liver enzymes

Reference:

  • Freo U, Ruocco C, Valerio A, Scagnol I, Nisoli E. Paracetamol: A Review of Guideline Recommendations. J Clin Med. 2021 Jul 31;10(15):3420. doi: 10.3390/jcm10153420. PMID: 34362203; PMCID: PMC8347233.
  • Caparrotta T M, Carduff E, Dear J W. Paracetamol use in adults BMJ 2023; 383 :e070753 doi:10.1136/bmj-2022-070753