Paracetamol : Therapeutic uses, Dosage & Side Effects
Paracetamol (Acetaminophen) is p-Aminophenol derivative. It inhibits prostaglandin synthesis in the CNS. It is used to treat many conditions such as headache, muscle aches, arthritis, backache, toothaches, colds, and fevers. It relieves pain in mild arthritis but has no effect on the underlying inflammation and swelling of the joint.
Dose : 500-1000 mg (Adult), 50 mg (infants), 80- 160 mg (children 1-3 years), 240-320 mg (children 4-8 years), 300-600 mg (children 9-12 years)
Route : Oral, IV, Rectal
Plasma Half-life : 2-3 hours
Duration of action : 3-5 hours after oral dose
Bioavailability : 63–89%
Chemical formula : C8H9NO2
IUPAC name : N-(4-hydroxyphenyl)ethanamideN-(4-hydroxyphenyl)acetamide
Trade name : Ofirmev, Tylenol, Crocin, Metacin, Paracin, Calpol, Ultragin, Pyrigesic, Neomol, Fevastin, Febrinil, Panadol,
Therapeutic uses : Paracetamol has following usage :
- Used as Antipyretic, analgesic agent. It has negligible anti-inflammatory action.
- It is suitable substitute for the analgesic and antipyretic effects of NSAIDs for those patients with gastric complaints/ risks, in those whom a prolongation of bleeding time is not desirable, as well as those who do not require the anti-inflammatory action of NSAIDs.
- It is the analgesic/antipyretic of choice for children with viral infections or chickenpox (due to the risk of Reye syndrome with aspirin).
- Paracetamol is one of the most commonly used ‘over-the-counter’ analgesic for headache, mild migraine, musculoskeletal pain, dysmenorrhoea etc. but is relatively ineffective when inflammation is prominent.
- It is recommended as first choice analgesic for osteoarthritis by many professional bodies.
- lt is one of the best drugs to be used as antipyretic, especially in children (no risk of Reye’s syndrome).
Why should we use Paracetamol instead of Aspirin ?
- Paracetamol is much safer than aspirin in terms of gastric irritation, ulceration and bleeding (can be given to ulcer patients), does not prolong bleeding time.
- Hypersensitivity reactions are rare.
- No metabolic effects or acid-base disturbances.
- Can be used in all age groups (infants to elderly), pregnant/lactatingwomen, in presence of other disease states and in patients in whom aspirin is contraindicated.
- It does not have significant drug interactions.
Thus, it may be preferred over aspirin for most minor conditions.
Side effects : In isolated antipyretic doses paracetamol is safe and well tolerated i.e At normal therapeutic doses, acetaminophen is virtually free of significant adverse effects.
Occasionally, Paracetamol may cause following Side effects :
- Nausea,
- Rashes,
- Leukopenia (rarely).
Acute Paracetamol poisoning : It occurs especially in small children who have low hepatic glucuronide conjugating ability. If a large dose (> 150 mg/kg or > 10 g in an adult) is taken, serious toxicity can occur. Fatality is common > 250 mg/kg. Early manifestations are just nausea, vomiting, abdominal pain and liver tenderness with no impairment of consciousness. After 12-13 hours centrilobular hepatic necrosis occurs which may be accompanied by renal tubular necrosis and hypoglycaemia that may progress to coma. Jaundice starts after 2 days.
Fulminating hepatic failure and death are likely if the plasma levels are above the line joining 200 pg/ml at 4 hours and 30 pg/ml at 15 hours. If the levels are lower -recovery with supportive treatment is the rule.
Contraindications :
- Paracetamol is not recommended in premature infants ( < 2 kg) for fear of hepatotoxicity.
- Acetaminophen should be avoided in patients with severe hepatic impairment.
For detailed query or in case of uncertainty, Always consult your doctor or pharmacist.
