Paracetamol (acetaminophen)

Paracetamol is effective by oral and parenteral routes. It is well absorbed, widely distributed all over the body, metabolized in liver by sulphate and glucuronide conjugation. The metabolites are excreted in urine.

Uses

1.As an antipyretic– reduces body temperature

2.as an analgesic to relieve headache , toothache, bodyache

2. Preferably used in asthmatics patients with peptic ulcers , hemophilia

Adverse effects

• Side effects are rare, occasionally causes skin rashes and nausea.
• Hepatotoxicity: with acute overdose or chronic use.
• Nephrotoxicity is commonly seen on chronic use.

Acute paracetamol poisoning

Acute overdose mainly causes hepatotoxicity the symptoms are –

nausea, vomiting, diarrhea abdominal pain, hypoglycaemia, hypotension, hypoprothrombinemia, coma, etc.

Death is usually due to hepatic necrosis.

Mechanism of toxicity and treatment

1.The toxic metabolite of paracetamol is detoxified by conjugation with glutathione and gets eliminated.

2.High doses of paracetamol cause depletion of glutathione levels. In the absence of glutathione, toxic metabolite (NAPQI) binds covalently with proteins in the liver and kidney and causes necrosis. Alcoholics and premature infants are more prone to hepatotoxicity.

3.N-Acetylcysteine or oral methionine replenishes the glutathione stores of the liver and protects liver cells.

4.Activated charcoal is administered to decrease the absorption of paracetamol from the gut. renal failure.

5.Haemodialysis may be required in cases with acute renal failure.

Source – textbook of pharmacology for dental students- Tara Shanbhag