Coumadin Mechanism of Action

Pharmacotherapeutic Group: Anticoagulant.
Pharmacology: Coumadin and other coumarin anticoagulants act by inhibiting the synthesis of vitamin K-dependent coagulation factors. The resultant in vivo effect is a sequential depression of Factors VII, IX, X and II activities. The degree of depression is dependent upon the dosage administered. Anticoagulants have no direct effect on an established thrombus, nor do they reverse ischemic tissue damage. However, once a thrombus has occurred, the goal of anticoagulant treatment is to prevent further extension of the formed clot and prevent secondary thromboembolic complications which may result in serious and possible fatal sequelae.
Pharmacokinetics: After oral administration of Coumadin, absorption is essentially complete, and maximal plasma concentrations (C_max) are reached in 1-9 hrs. Approximately 97% is bound to albumin within the plasma. An anticoagulant effect generally occurs within 24 hrs. However, peak anticoagulant effect may be delayed 72-96 hrs and its duration of action may persist for 4-5 days, thus producing a smooth and long-lasting response curve. Coumadin is metabolized by hepatic microsomal enzymes to inactive metabolites that are excreted into the bile, reabsorbed and excreted into the urine.
Coumadin is a potent drug with a t_½ of 2½ days; therefore its effects may become more pronounced as daily maintenance doses overlap.