 Let's continue on and compare and contrast warfarin and heparin and how they are like and how they differ. The route of administration for warfarin is orally. We give this as a pill form. Heparin, however, is intravenous or subcutaneous only. If we're in a hospital setting, we're likely going to give heparin via an IV as it is much easier to discontinue, but if we do send a patient home on a heparin, specifically a low molecular weight heparin, like an oxaparin or lovinox, then we'll send that home in a subcutaneous formulation that will be able to be injected into the belly. The mechanisms of action of warfarin and heparin do differ. Warfarin works on those vitamin K-defendant clotting factors, those specifically are 2, 7, 9, 10 protein C and protein S. Heparin, however, activates antithrombin, which we discussed how that works, that decreases the action of our 2A or our thrombin, as well as factor 10A. Warfarin works in the liver by working against that vitamin K-dependent clotting factors and keeping them from forming or synthesizing, whereas heparin works in the blood. It works directly on the clotting factors. With warfarin, it does take days. It's very slow for this to get to a point where you see action associated with warfarin, whereas with heparin, it's almost immediate. As soon as you begin giving it, especially if you give it IV, it's an immediate anticoagulation. The duration of action, however, warfarin lasts longer. It takes longer to start to become effective. It's going to take longer for it to get out of the system, so it's going to last longer, whereas heparin is only effective for hours. In order to reverse warfarin, all we have to do is give vitamin K, because it affects the vitamin K clotting factors. We give vitamin K, and we can reverse that effect. If we do need an acute situation or we need someone to immediately reverse the effects of warfarin, we can give fresh frozen plasma. To reverse heparin, we can just stop giving heparin, and we can see that effect very quickly. We do need to reverse it in emergency situations. We can use protamine sulfate. In regards to how we monitor heparin and warfarin, with warfarin, we're going to monitor the PT and the INR, which is mostly going to be checking our extrinsic pathway. Then with heparin, we will monitor the PTT, which is going to be monitoring our intrinsic pathway of the clotting cascade. One further thing that differs between heparin and warfarin is that warfarin is tritogenic. We cannot use this in pregnancy, whereas heparin is not tritogenic, so we can use this in a pregnant female or someone that is almost to give birth and has issues with clots.