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Should we be treating more patients with warfarin (Coumadin)?
Henry I. Bussey, Pharm.D., FCCP, FAHA
March, 2007
Reference: Glazer NL, Dublin S, Smith NL, et. al. Newly detected atrial fibrillation and compliance with antithrombotic guidelines. Arch Intern Med. 2007 Feb 12;167(3):246-52.
This article is one of several key studies* that are raising important questions about the future role of warfarin therapy, especially in patients with atrial fibrillation.
Is the expanded use of warfarin causing more harm than good, and should we reduce our use of anticoagulation in atrial fibrillation?
Should we be using warfarin to treat more, rather than fewer, patients with atrial fibrillation?
Does improving INR control beyond that typically reported in clinical trials yield an improved risk/benefit ratio? If so, what can be done to improve INR control further? If we can optimize INR control, will there be a need for newer anticoagulants currently in development?
What is the adherence rate of warfarin patients managed in an anticoagulation clinic, and are there clinical consequences of non-adherence in such patients?
The study by Glazer et. al. found that a sizeable percent of newly diagnosed, high risk atrial fibrillation patients still are not receiving warfarin therapy. Does this mean we should be treating more patients with warfarin?
The Group Health Cooperative of Seattle, Washington between October 1, 2001 and September 30, 2002 identified 572 patients between the ages of 30 and 84 years who were newly diagnosed with atrial fibrillation. Of the 572 patients, 437 were considered to be at high risk for stroke and only 257 of these (59%) received warfarin. These numbers are relatively consistent with numerous other reports that have found that only about one-half of atrial fibrillation patients who qualify for warfarin therapy actually receive it. This report further noted that of those who were receiving warfarin, their INRs were in range only about 48% of the time - a level of INR control that has been associated with more than a doubling in the rate of major events when compared to better INR control.1 In total, these results are especially troubling. In several of the pivotal atrial fibrillation trials, the risk of stroke was reduced by more than 80% based on on-treatment analysis with INRs within the target range about two-thirds of the time. From this report, it appears that this very beneficial treatment is being withheld from about 40% of patients and the remaining 60% are achieving about only one-half the benefit that could be achieved with better controlled warfarin. An editorial by David Green, MD, PhD cites a lack of anticoagulation clinics as a major reason why physicians are not using anticoagulation as recommended and suggest that establishing a network of such clinics in an important goal if optimal care is to be provided to these patients.2
Additional Questions About Warfarin's Future
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Should we be treating fewer patients with warfarin (Coumadin)?
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Can better INR control be achieved, and if so, how will new anticoagulants compare to warfarin (Coumadin)?
Additional References
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White HD, Gruber M, Feyzi J, et. al. Comparison of outcomes among patients randomized to warfarin therapy according to anticoagulant control: results from SPORTIF III and V. Arch Intern Med. 2007 Feb 12;167(3):239-45.
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Journal Watch Oncology and Hematology, Feb. 12, 2007
http://oncology-hematology.jwatch.org/cgi/content/full/2007/212/1
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