Moving to Generic Warfarin Could Affect Your INR

Publication Date: 
Sat, 08/17/2013
By: Alere Staff

The use of generic medications is very common in the United States.1 The U.S. Food & Drug Administration (FDA) reports that nearly 8 out of 10 prescriptions are filled with the generic form of the medications.2 All prescription and generic medications must meet the tough FDA standards in order to be available for use as substitute for a name brand medications.3 They must contain the same amount of the active ingredient, strength and purity of the name brand form. Also, they must be proven to be equally effective.

Coumadin® medication is the name of one of the brands of the anticoagulation medication that has been used for over 60 years. There are many different manufacturers that make generic Coumadin® medication, often called warfarin. Jantoven® tablet is a “name brand” generic form. When taking Jantoven® drug, you are getting the exact same generic preparation of warfarin every time.

Coumadin® medication has a narrow range of therapeutic effectiveness. This causes some concern as to whether the generic form warfarin is as effective as the name brand. Many studies have been done to look at this issue.1 Generic warfarin has been found to be safe and effective for patients to use.

There have been no studies comparing one generic form of warfarin to another so there is no way of knowing how you will respond. It is recommended that you fill your prescription at the same pharmacy to increase your chances of the same manufacturer of your warfarin tablets. You should also look beyond just the colors being the same. Manufacturers use the shape of the tablet to differentiate their warfarin product over another.

Because there are slight differences in the way the generic medications are made, you may see a slight variation in your INR when you switch from name brand to generic. Your doctor may want to test your INR after you switch to the generic. To be consistent, you should stick to using one form or the other rather than frequently changing back and forth between generic and name brand.

  1. Dentali F, et al. Warfarin Associated Research Projects and Other Endeavors (WARPED) Consortium. Brand name versus generic warfarin: a systematic review of the literature. Pharmacotherapy. 2011 Apr;31(4):386-93. doi: 10.1592/phco.31.4.386. Review. PubMed PMID: 21449627.
  2. U.S. Food & Drug Administration. Facts about Generic Drugs. Updated September 19, 2012. Retrieved July 8, 2013.
  3. 3Holmes DR, Jr, Becker JA, Granger CB, et al. ACCF/AHA 2011 Health Policy Statement on Therapeutic Interchange and Substitution: A Report of the American College of Cardiology Foundation Clinical Quality Committee. J Am Coll Cardiol. 2011;58(12):1287-1307. doi:10.1016/j.jacc.2011.06.001.


COUMADIN® is a registered trademark of Bristol-Myers Squibb Pharma Company. Alere is not affiliated or associated with Bristol-Myers Squibb Pharma Company or the COUMADIN® trademark.