Use of vitamin K antagonists

Is there still a place for vitamin K antagonists? When can they be used?

Mark Crowther, MD: There absolutely is still a role for vitamin K antagonists. Essentially, the role falls into 2 groups. There are a group of patients in whom we know the new agents should not be used, for example, patients with mechanical heart valves. And perhaps some patients with very profound hypercoagulable states should be treated with a vitamin K antagonist. For example, we have 60 years of experience using warfarin with mechanical heart valves with very good efficacy. The first valves were placed in 1960s and we have had patients who have been on warfarin, acenocoumarol, or phenprocoumon since then with good effect. So for patients with mechanical heart valves and perhaps a group of patients with other potent hypercoagulable states, the vitamin K antagonists are and will remain the treatments of choice.

The second group is patients who cannot afford the new agents. The new agents are not inexpensive. They are quite expensive in many jurisdictions and in many places patients cannot afford them. In the United States, for example, warfarin remains by far the most frequently prescribed blood-thinning medication predominantly because of cost issues. In Canada, where I work, warfarin is used relatively less now because the new drugs are both less expensive but also more widely available through drug plans that the government or private payers fund.

Warfarin and vitamin K antagonists will absolutely continue to have a role in selected patients and in patients who cannot afford the newer agents.