Paracetamol

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[edit] BRAND NAMES

[edit] STRUCTURE

Paracetamol.jpg

[edit] MECHANISM OF ACTION

Paracetamol is centrally acting analgesic and antipyretic agent with negligible anti-inflammatory properties.

Paracetamol is thought to produce analgesia by inhibiting prostaglandin synthesis centrally and elevating the pain threshold .

Studies have shown that endogenous pyrogens produced by leukocytes cause an elevation of prostaglandin E in the cerebrospinal fluid. Paracetamol reduces fever by blocking the formation and release of prostaglandins in the centralnervous system and inhibiting the action of endogenous pyrogens at the hypothalamic thermoregulatory centers

[edit] INDICATIONS

Paracetamol is indicated for the relief of minor aches and pains associated with the common cold, headache, toothache, muscular aches, backache, for the minor pain of arthritis, for the pain of menstrual cramps, and for the reduction of fever in infants, children, and adults

[edit] DOSAGE

  • Adults and children 12 years of age and older: the recommended dose is 500 to 1000 mg every 4 to 6 hours as needed, not to exceed 4000 mg in 24 hours
  • Children under 12 years of age: the recommended dose of acetaminophen is 10 to 15 mg/kg every 4 to 6 hours, not to exceed 50 to 75 mg/kg in 24 hours

[edit] CONTRAINDICATIONS

  • Hypersensitivity to paracetamol
  • Severe and active hepatic impairment

[edit] WARNINGS AND PRECAUTIONS

  • Paracetamol (Acetaminophen) has been associated with cases of acute liver failure, at times resulting in liver transplant and death. Most of the cases of liver injury are associated with the use of Paracetamol at doses that exceed 4000 mg/day. The risk of acute liver failure is higher in individuals with underlying liver disease and in individuals who drink alcohol while taking Paracetamol.
  • Hypersensitivity reactions to paracetamol: There have been post-marketing reports of hypersensitivity and anaphylaxis associated with the use of Paracetamol. Clinical signs included swelling of the face, mouth, and throat, respiratory distress, urticaria, rash, pruritus, and vomiting. In case a hypersensitivity reaction occurs, the drug should be discontinued.

[edit] INTERACTIONS

  • The anticoagulant effect of warfarin and other coumarins may be enhanced by prolonged regular daily use of paracetamol with increased risk of bleeding; occasional doses have no significant effect.


[edit] PHARMACOKINETICS

Paracetamol is rapidly and completely absorbed from the gastrointestinal tract after oral administration with peak plasma levels occurring 30 to 60 minutes after administration. It is metabolised in the liver and excreted in the urine mainly as the glucuronide and sulphate conjugates. Less than 5% excreted as unchanged Paracetamol.

The elimination half-life varies from about 1 to 4 hours. The apparent volume of distribution is 1 to 1.2 L/kg. Plasma protein binding is negligible at usual therapeutic concentrations but increases with increased concentrations. Paracetamol can cross the placenta and excreted in milk. Food intake delays paracetamol absorption.

[edit] PREGNANCY AND LACTATION

  • Pregnancy: Acetaminophen is routinely used during all stages of pregnancy and is categorized with FDA as Pregnancy Category B (US). Adequate and well-controlled studies in pregnant women have failed to demonstrate a risk to the fetus in any trimester
  • Nursing mothers: Paracetamol is excreted in breast milk in small amounts, but the significance of its effect on nursing infants is not known. Because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.

[edit] SIDE EFFECTS

Adverse effects of paracetamol are rare and usually mild, although haematological reactions have been reported. Skin rashes and other hypersensitivity reactions occur occasionally.

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