The full dose of Pentasa is 4 grams...if you have been on the full dose for more than four weeks, and yet are still in flare, then it makes sense to look at other meds.
Antibiotics like Cipro and Flagyl might help...you have battled this dang disease for a long time, so you probably already know about them. And know that they are not that effective for most people.
So, to quickly arrest a full flare, that leaves pred or Entocort. Pred is quick, but Entocort could take weeks to reach full effectiveness. Also, it works only for Crohn's localized in the terminal ileum. That said, Entocort has been wonderful for my daughter.