Biogesic Mechanism of Action

Analgesic/antipyretic.
Pharmacology: Mechanism of Action: Paracetamol exhibits analgesic and antipyretic activity by inhibiting prostaglandin synthesis. It produces analgesia by elevating the pain threshold and antipyresis through action on the hypothalamic heat-regulating center.
In therapeutic doses, paracetamol's analgesic and antipyretic action is comparable to that of aspirin. Paracetamol does not adversely affect platelet function and hemostasis.
Pharmacokinetics: Paracetamol is rapidly and completely absorbed after oral administration. Peak plasma concentrations occur between 15 min to 2 hrs after ingestion. The absolute oral bioavailability of paracetamol is about 80% and is independent of dose in the range of 5-20 mg/kg.
Paracetamol is not bound to plasma proteins to any extent. The concentrations of paracetamol in saliva are similar to those in plasma. Concentrations in whole blood are up to 20% higher and in breast milk about 20% lower than the plasma concentration. Paracetamol crosses the placenta.
Paracetamol is extensively metabolized in the liver and the total body clearance is about 5 mL/kg/min. The clearance of paracetamol is reduced and the half-life is increased following a hepatotoxic overdose. Prolongation beyond 4 hrs usually indicates impending liver damage.
Two to five percent of a therapeutic dose of paracetamol is excreted unchanged in the urine. Its renal clearance is about 10 mL/min and is weakly dependent on urine flow rate but not on pH.