Warfarin, NOACs and Reversal Agents

Warfarin has been in use effectively treating blood clots since 1955.1 We know warfarin, we understand it and are comfortable with how to advise therapies around it. We are able to measure the effectiveness of the drug with a simple INR blood test that has been even further simplified with the ability to test at home. We also have a solid enough understanding of interactions, enabling us to often predict the effect on the INR for proactive warfarin dosing.

Reversal agents

While it may not be desirable to undo or reverse the effects of an anticoagulant, it is reassuring to know it can be done if necessary. Warfarin has been around for over 60 years, allowing for the development of more clinical experience with the drug.2 Over the years, physicians have been able to create guidelines for management, monitoring and reversal with vitamin K or plasma factors. Vitamin K, administered through a variety of routes, has long been the antidote for warfarin if one’s INR is very elevated or in other words, the blood is dangerously ‘too thin’.3 This medication is, of course, prescribed by your physician when appropriate.

Such experience and guidance are not currently available for the New Oral Anticoagulants (NOACs). Clinicians and patients alike have expressed two main concerns about NOAC drugs: not having a reversal agent and the inability to determine the extent of anticoagulation as one can with the INR test for warfarin.4 The tests that may assist in proper dosing are either not widely available or may not be available in the time required.2,4 Meanwhile, there are very limited reversal agents available for the NOACs and guidelines as to how to work with them.2,4 For now, supportive therapies such as IV administration of blood products are employed in extreme situations for patients on the newer drugs.

There are many factors that play into making a choice between warfarin and a NOAC for anticoagulation. Armed with all the information you need, it’s wise to discuss this complex decision with your health care provider to find the solution that best meets your individual needs.

References:

  1. Hanley, Colleen M., Kowey, Peter R., (2015). Are the novel anticoagulants better than warfarin for patients with atrial fibrillation? Journal of Thoracic Disease, 5;7(2): 165-171. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4321074.
  2. Hu, T.Y. et al. Reversing anticoagulant effects of novel oral anticoagulants: role of ciraparantag, andexanet alfa, and idarucizumab. Vasc Health Risk Manag. 2016; 12:35-44. Retrieved from the website: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4762436/
  3. DeSantis, G., et al. (2014). STABLE Results: Warfarin Home Monitoring Achieves Excellent INR Control. The American Journal of Managed Care.