I know there's another thread that addresses this, and I think the magic number for the decrease in arimidex, because of nolvadex, was 27%(?) in blood plasma levels. (I know I'm messing up the structure and terminology, but hopefully you get what I'm trying to say.)

That said, couldn't you just up the dose from 50mg to 75mg to account for the decrease?

If there's something I'm missing let me know.