Current use of warfarin

Dr Mark Crowther is a professor and chair of the Department of Medicine and the Leo Pharma Chair in Thromboembolism Research at McMaster University.

Can warfarin be called an obsolete treatment?

Mark Crowther, MD, MSc: Warfarin and the other oral vitamin K antagonists are extremely difficult drugs to use. They are associated with a high risk of highly undesirable bleeding, including intracerebral bleeding, but they still have a role to play. The role falls into 2 different areas.

The first is, there are patients with selected states where warfarin remains the preferred agent. The two that are most frequent are mechanical heart valves—which are not related to venous thromboembolism (VTE) but are an indication for anticoagulation—where it’s very clear that a patient with mechanical heart valve should be treated with warfarin.

The second is in selected very high-risk states for recurrent thrombosis. The most important one is antiphospholipid antibody syndrome (APS), where work published by a group out of Italy in a study called the TRAPS (Trial on Rivaroxaban in AntiPhospholipid Syndrome)—a study published last year in Blood—demonstrated that in very high-risk APS patients warfarin was both safer and more effective than rivaroxaban for the prevention of recurrent VTE.

So warfarin and the other vitamin K antagonists do continue to have a role in selected high-risk states. The other [reason why] warfarin still has a role to play and why it is used extensively in many countries is that it is very cheap. And for many patients and in many health-care systems cost is a very important consideration. For example, in the United States, where cost of medications is a real issue, warfarin is by far the cheapest of all the different therapeutic options and as a result of that continues to be widely used.