I have been on imuran for 4 years. It has been around for AI diseases and transplants for decades and most patients tolerate it much better than prednisone. Like all meds, some do not. Doctors are very familiar with it problems and benefits.
My experience has been mostly good. No side effects at all for 18 months then it hit my wbc, rbc and platelets. After lowering the dose it has been fine....no problems. Some patients experience an intolerance almost immediately and withdraw.
Personally, I would not hesitate to use it if my doctor wanted it. It takes 4-6 months to become fully effective.
Bill