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Knowledge At MET

Knowledge At MET

Acetaminophen Toxicity

Drug Testing Advisory Board (DTAB) recommended limiting the amount of paracetamol in prescription combination products to not more than 325mg per tablet or capsule . It gave warning of potential severe liver injury and allergic reaction (eg. swelling of face, mouth and throat, difficulty in breathing, itching, rash).

Paracetamol (PCM) is widely available and has been under clinical use since the 1950s. It is a safe drug and also widely prescribed. Being a common OTC drug, it is often taken in excess. The maximum tolerable dose PCM is approximately 4 gm/day.

Paracetamol overdose can be:

  • Planned overdose- sometimes people take too much PCM on purpose to harm
  • Unplanned overdose (accidental) - taking too much or for too many days in a row; taking more than one concomitant medicine at a time(all of which may contain PCM); taking extended release forms PCM toxicity can be asymptomatic at first. However, as it progress, the following clinical

picture is seen:

Damage to liver (hepatotoxicity), results from PCM and its metabolites, N-acetyl-p-benzoquinone imine (NAPQI). NAPQI depletes the liver’s natural antioxidant glutathione and directly damages liver cells, leading to liver failure.

Treatment is aimed at removing the PCM from the body and replacing glutathione. Other methods include:

  1. Gastric
  2. Use of activated charcoal to adsorb acetaminophen within one hour of its
  3. Antidote acetylcysteine acts as a precursor for glutathione and also supplies thiols that function as antioxidants, helping the body regenerate enough to prevent damage to the

Patient counselling and role of Pharmacist:

  • Educate the patient about the maximum permitted dose per 24 hours (i.e. 8 tablets of 500mg each with spacing of 3 hours) and associated liver toxicity with long terms use of
  • Check all prescriptions for multiple products containing
  • Do not take PCM for more than 10 days to treat pain or for more than 3 days to treat a fever, unless prescribed by
  • Inform patients to read label carefully and identify the active ingredients, so that they can keep a check whenever they are using more than one OTC products
Dinesh M Choudhary (T Y B Pharm)

Tags: MET Institute of Pharmacy