Heparin vs. Warfarin: Key Differences

Heparin is a parenteral anticoagulant given intravenously or subcutaneously that works immediately by activating antithrombin three, which inhibits thrombin and factor ten-a. Warfarin is an oral anticoagulant that takes three to five days to reach full effect because it works by depleting vitamin K-dependent clotting factors. Heparin is monitored by activated partial thromboplastin time, or aPTT, while warfarin is monitored by INR. Heparin is reversed by protamine sulfate, while warfarin is reversed by vitamin K.