Sulfasalazine used to be the go-to drug when I was first diagnosed - getting close to 40 years now.....it initially worked well for me, for years, would put me into remission. Over time, the remission periods would get shorter and shorter and eventually I moved on to stringer drugs. Mind you, back then, it was common practice to be put on medication until remission was achieved, then taken off of it until another flare occurred. This is different thinking than these days where maintenance dosages are much more common.
Couldn't tell you if Pentasa would be more effective, that is an individual experience.