Anzatax Mechanism of Action





Zuellig Pharma


Full Prescribing Info
Pharmacology: Paclitaxel is an antimicrotubule antineoplastic agent. It promotes microtubule assembly by enhancing the polymerisation of tubulin, the protein subunit of spindle microtubules, even in the absence of the mediators normally required for microtubule assembly (e.g. guanosine triphosphate [GTP]), thereby inducing the formation of stable, nonfunctional microtubules. While the precise mechanism of action of the drug is not completely known, paclitaxel disrupts the dynamic equilibrium within the microtubule system and blocks cells in the late G2 phase and M phase of the cell cycle, inhibiting cell replication and impairing function of nervous tissue.
Pharmacokinetics: After paclitaxel is administered intravenously, its plasma concentration declines biphasically. The first phase shows rapid decline representing distribution of paclitaxel to the peripheral compartment and elimination. This initial phase is followed by a relatively slow elimination of paclitaxel from the peripheral compartment.
The following ranges for the pharmacokinetic parameters have been determined in patients given doses of 135 and 175 mg/m2 as 3 hour and 24 hour infusions of paclitaxel: mean terminal half life: 3.0 to 52.7 hours; total body clearance: 11.6 to 24.0 L/h/m2; mean steady state volume of distribution: 198 to 688 L/m2.
These indicate extensive distribution of paclitaxel outside the vascular system and/or tissue binding. The following mean values for the pharmacokinetic parameters have been reported following a three hour infusion of 175 mg/m2 paclitaxel: mean terminal half life: 9.9 hours; mean total body clearance: 12.4 L/h/m2; The serum protein binding of paclitaxel is 89%.
The liver is thought to be the primary site of metabolism for paclitaxel. The mean cumulative urinary recovery of unchanged paclitaxel has been reported as 1.8 to 12.6% of the dose.
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