Pharmacotherapeutic group: Other analgesics and antipyretics. ATCvet code: QN02BE01
Pharmacodynamic properties
Paracetamol, or acetaminophen is a para amino-phenol derivative with analgesic and antipyretic properties. Its antipyretic effect may be explained by its ability to inhibit brain cyclo-oxygenases. Paracetamol is only a weak inhibitor of COX-1 synthesis and, thus, has no gastrointestinal side-effects and has no effect on platelet-aggregation.
Pharmacokinetic properties
Absorption and distribution
After a single oral administration of Pracetam in feed, at 15 mg/kg, the bioavailability is 76%, the peak of paracetamol concentration (Cmax), 3.6 µg/ml, is reached 2.4 hours after the administration.
Metabolism
Paracetamol is metabolised mostly in the liver. The two major metabolic pathways are glucuronide conjugation and sulphate conjugation. A minor pathway catalysed by CYP (cytochrome P450) leads to the formation of the intermediary reagent, N-acetyl benzoquinoneimine which is rapidly detoxified by reduced glutathione and removed in urine after conjugation with cystein and mercapturic acid.
Elimination
Paracetamol is essentially eliminated through urine (70% of a single dose is eliminated via urine within 24 hours) under the form of paracetamol glucuronide (80%). The other forms of elimination are cystein (10%), unchanged paracetamol and sulphate.