Anticoagulant medications include:

The two standard anticoagulants used are heparin and warfarin. These two medications act somewhat differently to accomplish the same thing: inhibiting the growth of existing blood clots or preventing the formation of new ones.

Studies find that even low-dose warfarin, an oral medication that acts by inhibiting blood clotting factors that depend on vitamin K, can be effective in reducing the risk of recurrence of blood clots, especially in patients with a history of deep vein thrombosis and previous heart attack. This also applies to those at risk of deep vein thrombosis, including patients undergoing hip or leg surgery.

Heparin, by contrast, acts by indirectly inhibiting thrombin, a component of blood that is critical to clotting. Newer forms of heparin, called low-molecular-weight heparin, have been developed that are more predictable in their anticoagulant effect and do not need to be monitored in a therapeutic setting.

However, both warfarin and heparin have drawbacks that have prompted researchers to search for new anticoagulants. The two largest drawbacks are their relatively narrow window of effectiveness before the risk of bleeding, and their highly variable nature among individuals. Typically, anticoagulation therapy has required very close laboratory monitoring as physicians attempt to walk the fine line between adequate anticoagulation and an elevated risk of bleeding.

Newer anticoagulants are being studied. In general, these medications act in a similar fashion to heparin or warfarin, but are hopefully more predictable and do not require close laboratory monitoring. Some of the newer anticoagulants include: