There's also a possibility that he's sensitive to the asacol. There's a small minority of us who can't take it because it gives us terrible diarrhea and pain. If so, they can try another of the available drugs. For instance, I can tolerate both Pentasa and Colazal, but not Asacol. Sometimes it takes a bit to find the proper dosage and combination.
But fever, yes, you definitely need to call the doctor. That suggests an infection and isn't usual with a UC flare.
Left-sided UC diagnosed 2001. Taking Colazal and Imuran, Remicade infusions and moving into remission. Finally off steroids after four years!
Now in remission for almost two years. Remicade has been my wonder drug.
"If you spend your time second-guessing your past decisions, you'll never have time to enjoy today."