I have been on Azathioprine before and now I am on 6mp, which is the sister drug. (My new GI doctor has a preference for 6mp.) It took 4 months for the Azathioprine to work and I had to go on Prednisone until the Azathioprine kicked in. Once it did, it worked well and I had no side effects. When you are on these medications you need to get your blood tested frequently to check your blood count and your liver function. I hope your husband can persevere and the drug will help him. If not, then it will be wise to consider one of the biologic medictions -Remicade, Humira, or Cimzia.