Haematology Watch


- The most frequently prescribed oral anticoagulant

- Mechanism of action:

          Therapeutic dose --> Carboxylation of synthesizing factors impaired --> Vitamin K antagonism --> 30 -50% synthesis

                                                 of factor II, VII, IX, X, and of endogenous anticoagulants Protein C & S.

                                           --> Carboxylation of secreted factors impaired --> functional deficiency of factors.

- Pharmacokinetics:

          Reaches plasma in 1 hr; peaks in 2 - 8 hrs.

          99% bound to albumin

          Metabolized in liver and kidneys: inactive metabolites secreted in urine and stool

          Mean t1/2: 40 hrs

          Duration of effect 2 - 5 days

          After impairing the release of new factors, the anticoagulant effect depends on the t1/2 of already circulating normal


                            Protein C     8 hrs    

                            FVII               6 hrs

                            FII                 50 hrs

- Effects:

         Anti-coagulant (Preventive)

         Anti-thrombotic (Therapeutic)