Pentasa is a very mild drug, as Kerri said. It rarely has side effects, but sometimes does not work all that well. Still, because it has so few side effects, doctors sometimes like to start with it first to see if it works. If it doesn't work after about 3 weeks or so, in my experience, they usually add something else such as prednisone; Pentasa is much milder than prednisone or other steroids. If your DH has not responded well to steroids in the past, Pentasa might work slowly or not at all, but it shouldn't hurt him and is certainly worth a shot before trying something stronger. There are also immunosuppressant meds such as Imuran, 6mp, and Remicade which are what they go to if neither Pentasa-type medications nor steroids work.

Other medications which are closely related to Pentasa are Asacol, Dipentum, Azulfadine, and Colazal. If your DH's doctor switches him from Pentasa to one of those for whatever reason, it pretty much is a switch to a different formulation of the same drug. FYI

Good job getting your DH to go to the doctor. Maybe you can get mine to go to the dentist.