I haven't found Pentasa to be too different from Asacol, but if your doctor thinks it will work well for you then it could be worth a try, especially if you still carry on with asacol suppositories.
It's a tough call to make when you're symptom free and then told to change meds, and up to you whether you're willing to take that risk.
Rio, 33 year old male. Diagnosed with UC in 2006
100 mg Azathioprine, 4800 mg Asacol
VSL#3 x 3 times a day, Metamucil wafers
Vitamin E enema or Mesacol/Asacol enema at least once a week
Spinach & sunflower seed diet