Hello Mypoeticsin..... First, welcome to the site. Im fairly new myself and have found it very helpful.
I just wanted to let you know that I am also on Pred. and just got my prescription for Imuran filled the other day and will be starting it soon. I will be taking 40mg Pred. and 150mg Imuran. From what I can see, it is fairly common to be on both but usually when you start Imuran, I do believe that you start tappering off the Pred. My GI told me that once I start Imuran that I am to tapper off 5mg a week from the Pred.
Anyways, hope that helps.