Take heart. I was put on 300mg daily of Allopurinol at the age of thirty three to reduce my uric acid level and prevent gout. That was in 1973!
My aircrew medical cat. was reduced to A2G2Z1 from A1G1Z1 simply to alert any medic who saw my documents. It was not a problem in any way to getting and holding a Class one medical with the CAA and FAA for many years.
I did hear that the only side effects from this drug seem to be beneficial and I haven't had a twinge of that excruciating pain in my big toe joint since 1973!