I happened to run into this yesterday in the ER at a local hospital while doing observations for my EMT course work.
A patient was on anticoagulation therapy and there was a discussion (briefly) as to whether she was taking Coumadin or warfarin. I said I thought it didn't make a difference and the nurse said not neccesarily.
A little later, I asked her to expand on that and she said that the absorbtion rates from brand to generic can differ and that would effect how the medication worked within one's system, how much dose they would need for the proper effect.
Now, I suppose you could take that a step further to say that it would also depend on a given individual's metabolism then. If your body absorbs medications faster/more efficiently than mine does, then it seems obvious that you might require less coumadin than I do to get the same INR range even though we (hypothetically) have the same weight, same height, same body type, and same eating habits...
Seems to me that the key is just consistancy. You want to get generics for the cheaper price, fine. You may have a few rocky INR levels until your body adjusts to the change in "formulations" of the active ingredients in the medication, but in the end you should be able to balance out if you stay consistant to one specific source of medication. Now if you're taking Coumadin one month and a generic warfarin the next, there may be a lot of fluctuation in your INR's...
I started out on Coumadin while at CCF and was switched (mainly by my pharmacy's preferences towards generics whenever not specifically told to use brand names) to warfarin when I got my first refill. I've been on the Barr warfarin ever since with minimal adjustments required to maintain my INR.
