Is There Still a Case for Warfarin?

With the U.S. availability of three novel oral anticoagulants (NOACs), is there any reason to still prescribe warfarin to treat patients with atrial fibrillation (AF) at increased risk for stroke? The limitations of warfarin are well known, and there at least ten advantages to NOACs compared to warfarin. For example, NOACs…

1. Do not require protime monitoring; 
2. Have a predictable anticoagulant effect;
3. Have limited interactions with other medications;
4. Have no interaction with food;
5. Are as effective at preventing stroke compared to warfarin;
6. Are less likely to cause intracranial hemorrhage compared to warfarin;
7. Are more convenient in preparation for cardioversion;
8. Do not require heparin bridging;
9. Are recommended by societal guidelines;
10. Have potential for patient-guided dosing.

A meta-analysis published in The Lancet last year highlighted the benefits of NOACs over warfarin, and found that the number of patients needed to treat to prevent one death and one intracranial hemorrhage over 2.2 years is 128 and 132, respectively.¹

So why is warfarin still prescribed? The reason is that despite the advantages of NOACs, there are still some situations when it is reasonable to prescribe warfarin to prevent stroke in patients with AF. One obvious reason is that there are patients with AF who were not represented in the NOAC clinical trials, including patients who have valvular AF. Nonvalvular AF is defined in the recent 2014 guidelines as “AF in the absence of rheumatic mitral stenosis, a mechanical or bioprosthetic heart valve, or mitral valve repair.”² Therefore, patients with rheumatic AF should continue to be treated with warfarin. 

Another reason to still prescribe warfarin instead of a NOAC for AF is cost. Although many insurance companies now cover the costs of at least one NOAC, cost continues to be a factor. Other reasons are the concerns about using NOACs in the very elderly, as well as the inability to reverse the anticoagulant effect of NOACs in the event of major bleeding. Some patients also just prefer to take warfarin after doing their own investigation. Finally, there is little evidence that switching a patient, who has been taking warfarin for years and is always in the therapeutic range, to a NOAC is to their advantage. NOACs appear to offer the most benefit to patients who are naïve to oral anticoagulation or have been taking warfarin and spend a large part of their time outside of the therapeutic range.

Therefore, despite all of the data that demonstrate the safety and efficacy of the NOACs, there are still times when warfarin should be prescribed.

References

1. Ruff CT, Giugliano RP, Braunwald E, et al. Comparison of the efficacy and safety of new oral anticoagulants with warfarin in patients with atrial fibrillation: a meta-analysis of randomised trials. Lancet. 2014 Mar 15;383(9921):955-962. Epub 2013 Dec 4.
2. January CT, Wann LS, Alpert JS, et al. 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol. 2014 Mar 28. doi: 10.1016/j.jacc.2014.03.021. [Epub ahead of print]