Hi, I had the same problem with my Azathioprine and the doctor's plan was to cut the dose from 175mg to 50mg and put me on Allopurinol 200mg. He said that the Allopurinol reacts with the Aza and makes it work more efficiently at a lower dose therefore not affecting liver function or blood count. I have been trying it now for the past two weeks, I am also tapering on prednisolone from 60mg down 10mg every two weeks to eventually none at all (yeah!) have to have bllod taken next week and have an appointment at the hospital on the 14th to see if his plan is working and I can stay on the Aza. Don't know if this will help you but maybe you could mention the combination of drugs to your GI.