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Novel Anticoagulants Should not Replace Warfarin; Head-to-Head Trial Needed

Marie Bussey
Henry I. Bussey, Pharm.D.
September, 2012

Three recent publications in Circulation suggest that well-managed warfarin may be superior to novel anticoagulant agents for prevention of thromboembolic events. Existing clinical trials of novel anticoagulants have shown the new agents to be non-inferior or even marginally superior to warfarin, but existing trials have compared the new agents to poorly managed warfarin only. The three publications described below suggest that well-managed warfarin may be safer and offer better outcomes than the new agents and that well-managed warfarin is attainable.

First publication (1): In January, 2012, ClotCare Editorial Board Member, Dr. Jack Ansell, published an article in Circulation in which he provided thorough support for the position that the new oral anticoagulants should not replace warfarin as first-line therapy for stroke prevention in atrial fibrillation. Among the numerous concerns that Dr. Ansell addressed is the fact that warfarin patients with good INR control had lower event rates than patients on novel anticoagulants in the available trials.

Second publication (2): In July, 2012, Christensen, Hasenkam, and Larsen from Denmark published a letter in reference to Dr. Ansell's article in which they describe one analysis in which therapy with dabigatran was no better than warfarin in patients whose INR time in range was greater than 65%. They also suggest that with INR self testing or self management, the INR time in range can be improved to at least 70%.

Third publication (3): Also in July, 2012, ClotCare Sr. Editor, Dr. Henry Bussey and ClotCare Lay Editor, Marie Bussey, published an article on INR self testing and self management in the "Cardiology Patient Page" section of Circulation. This article contends that INR self testing and warfarin self dosing certainly may improve INR control, but this INR control may be improved even further with online management. In fact, two small studies that combined INR self testing with online management reported an 80% time in range and, perhaps even more importantly, virtually eliminated INRs at the extremes of less than 1.5 or greater than 5, which is where events are most likely to occur.

These 3 publications raise several important issues. The first publication points out that the warfarin management was sub-optimal in the existing clinical trials of warfarin versus the new agents. The second publication emphasizes the value of warfarin therapy if the INR is well controlled and suggests that the 70% INR time in range achieved with self testing and self management might yield results superior to the new agents. The third publication suggests that combining online management with self testing and/or self dosing can improve INR control even further, perhaps to 80% time in range or better. While these publications point to evidence that well-managed warfarin may be superior to novel anticoagulants, no such head-to-head trial exists. As such, a randomized, control trial of optimally managed warfarin versus the new agents is clearly needed.

References:

  1. Ansell, J. New oral anticoagulants should not be used as first-line agents to prevent thromboembolism in patients with atrial fibrillation. Circulation. 2012 Jan 3;125(1):165-70.

  2. Christensen TD, Hasenkam JM, Larsen TB. Letter by christensen et Al regarding article, "new oral anticoagulants should not be used as first-line agents to prevent thromboembolism in patients with atrial fibrillation". Circulation. 2012 Jul 24;126(4):e45.

  3. Bussey HI, Bussey M. Warfarin management: international normalized ratio self-testing and warfarin self-dosing. Circulation. 2012 Jul 31;126(5):e52-4.
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