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Pharmacotherapeutic Group: Hapacol: Other Analgesics and Antipyretics - Anilides. Hapacol Junior: Other Analgesics and Antipyretics. ATC Code: N02BE01.
Pharmacology: Pharmacodynamics: Paracetamol is an effective analgesic and antipyretic agent. The drug has no effect on the cardiovascular and respiratory systems, and it does not cause gastric irritation or bleeding like salicylates.
Pharmacokinetics: Hapacol: Paracetamol is readily absorbed from the gastro-intestinal tract with peak plasma concentrations occurring 30 minutes to 2 hours after ingestion. It is distributed in most body tissues; it crosses the placenta and is present in breast milk. Plasma protein binding is negligible at usual therapeutic concentrations but increases with increasing concentration. The elimination half life varies from about 1 to 3 hours.
Paracetamol is metabolised in the liver and excreted in the urine mainly as the glucuronide and sulphate conjugates. Less than 5% is excreted unchanged as paracetamol. A minor hydroxylated metabolite which is usually produced in very small amounts by mixed-function oxidases in the liver and which is usually detoxified by conjugation with liver glutathione, may accumulate following paracetamol overdosage and cause liver damage.
Hapacol Junior: Absorption: The absorption of paracetamol by the oral route is complete and rapid. Maximum plasma concentrations are reached 30 to 60 minutes after ingestion.
Distribution: Paracetamol is distributed rapidly in all tissues. Concentrations are comparable in blood, saliva and plasma. Plasma protein binding is low.
Metabolism: Paracetamol is metabolized primarily in the liver. The two major metabolic pathways are glycuroconjugation and sulphoconjugation. The latter pathway is rapidly saturable at dosages above therapeutic doses. A minor route, catalyzed by cytochrome P450, is the formation of a reactive intermediate (N-acetyl benzoquinone imine), which under normal conditions of use, is rapidly detoxified by reduced glutathione and eliminated in the urine after conjugation with cysteine and mercaptopuric acid. On the other hand, during mass poisoning, the quantity of this toxic metabolite is increased.
Elimination: The elimination is essentially urinary. 90% of the ingested dose is eliminated by the kidney in 24 hours, mainly in glycuroconjugate (60-80%) and sulfoconjugate (20-30%).
Less than 5% is eliminated as unchanged.
The elimination half-life is about 2 hours.
Pathophysiological changes: Renal insufficiency: In patients with severe renal insufficiency (creatinine clearance less than 10 ml/min), the elimination of paracetamol and its metabolites is delayed.
Elderly: The conjugation capacity is not modified.
