Imuran again!

20 yrs ago during the first year of my diagnosis my neurologist tried me on Imuran. I wasn't even done with 30 day supply when he stopped it. Now twenty years later I requested Vyvgart for my weakness & fatigue. All I take now is mestinon. He said Let's try Imuran for a year and then evaluate for Vyvgart. He had completely forgot about the problems I had the first attempt.
Any advice is welcomed, before I go postal