Vasola Mechanism of Action

Pharmacology: Pharmacodynamics: Mechanism of Action: Fondaparinux is a synthetic and selective inhibitor of activated Factor X (Xa). The antithrombotic activity of fondaparinux is the result of antithrombin III (ATIII) mediated selective inhibition of Factor Xa. By binding selectively to ATIII, fondaparinux potentiates (about 300 times) the innate neutralization of Factor Xa by ATIII. Neutralisation of Factor Xa interrupts the blood coagulation cascade and inhibits both thrombin formation and thrombus development. Fondaparinux does not inactive thrombin (activated Factor II) and has no known effect on platelet function.
Pharmacodynamic Effects: At the 2.5 mg dose, fondaparinux does not have a clinically relevant affect on routine coagulation test, such as activated partial thromboplastin time (aPTT), activated clotting time (ACT) or prothrombin time (PT)/lnternational Normalised Ratio (INR) tests in plasma, nor bleeding time or fibrinolytic activity. Fondaparinux does not cross-react with sera from patients with Heparin induced thrombocytopenia (HIT) type II.
Anti-Xa activity: The pharmacodynamic/pharmacokinetics of fondaparinux are derived from fondaparinux plasma concentrations quantified via anti factor Xa activity. Only fondaparinux can be used to calibrate the anti-Xa assay. The international standards of heparin or low molecular weight heparin (LMWH) are not appropriate for this use. As a result, the concentration of fondaparinux is expressed as milligrams of the fondaparinux calibrator/litre.