Ask Dr. Stephan Moll

These questions have been submitted by folks on the mailing list and answered by Dr. Moll, Director of the Thrombophilia Program at the Carolina Cardiovascular Biology Center, Department of Medicine, Division of Hematology-Oncology, UNC Chapel Hill (North Carolina, USA). Why am I doing this?

29. Generic warfarin versus brand coumadin®

Q1 "My mom was on generic warfarin and her hemo Dr. took her off it; said it's not as effective as coumadin."
A1: It is not correct that generic warfarin is less effective than brand coumadin. Both are equally effective.

Q2: "Is it o.k. to switch from brand coumadin to generic warfarin? Is there a difference between the two?"
A2: It is o.k. to switch. They both contain the same active drug, i.e. warfarin. The drugs may differ minimally in their composition, but in most patients this is not clinically relevant.

Q3: "My own experience with generic is that I couldn't keep my INR stable. It jumped all over the place. I tried it for several months thinking I just had a bad month. As soon as I stopped taking it and went back on the real thing -my INR became stable. It's been stable for years now.
A3: There may be an occasional patient in whom generic warfarin causes INR fluctuations, and in this patient it may be worth trying brand coumadin to see whether the INR fluctuations improve. For other causes of INR fluctuations see Q/A 27.

Q4: "My experience with warfarin was not great, I could not keep my INR stable. I am having better luck with coumadin, but it still goes crazy sometimes!!"
A4: see A3

Q5: "My INR was all over the place with coumadin (just after diagnosis) for about 6 months; stable on generic warfarin for 2 years now."
A5: It is often difficult to discern whether it is really the type of drug one takes (generic warfarin versus brand coumadin) or something else that makes the INR fluctuate. In this patient one could conclude that generic warfarin causes less INR fluctuations than brand coumadin, but may be he/she just got used to taking an oral anticoagulant and eating a more steady diet and being knowledgeable about medications that can interact with warfarin.

Available clinical data indicate that generic warfarin and brand coumadin are equally effective and can be exchanged for one another [reference 1]. In a patient with fluctuating INRs all causes of fluctuation should be considered (see Q/A 27). If none of the causes apply, then it is worthwhile to switch the patient to brand coumadin and see whether the fluctuations ease or disappear.

Reference:

1. Southern Medical Journal 2001;94:16-21

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