Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1 Pharmacodynamic properties
Pharmacotherapeutic group: Other analgesics and antipyretics.

ATC code: N02B E01
Mechanism of Action
Analgesic – the mechanism of analgesic action has been fully determined. Paracetamol may act predominantly by inhibiting prostaglandin synthesis in the central nervous system (CNS) and to a lesser extent, through a peripheral action by blocking pain-impulse generation.
The peripheral action may also be due to inhibition of prostaglandin synthesis or to inhibition of synthesis or actions of other substances that sensitize pain receptors to mechanical or chemical stimulation.
Antipyretic – paracetamol probably produces antipyresis by acting centrally on the hypothalamic heat-regulation center to produce peripheral vasodilation resulting in increased blood flow through the skin, sweating and heat loss. The central action probably involves inhibition of prostaglandin synthesis in the hypothalamus.

Pharmacokinetic Properties

5.2 Pharmacokinetic properties
Paracetamol is rapidly and almost completely absorbed from the gastrointestinal tract with peak plasma concentrations occurring about 30 minutes to 2 hours after ingestion. Plasma protein binding is negligible at usual therapeutic concentrations but increases with increasing concentrations. The elimination half-life varies from about 1-4 hours.
Paracetamol is metabolized predominantly in the liver and excreted in the urine mainly as the glucuronide and sulphate conjugates. Less than 5% is excreted as unchanged paracetamol.
A minor hydroxylated metabolite which is usually produced in very small amounts by mixed function oxidases in the liver and kidney which is usually detoxified by conjugation with liver glutathione, may accumulate following paracetamol over dosage and cause liver damage.