Mezavant is a brand name for mesalamine, and I believer Salofalk also is mesalamine. It's a very good drug, and usually the first tried for UC. But a significant number of people don't tolerate it, and it can cause increased symptom in them. In this case, usually a different drug is used. In my case, I was put on Colazal (balsalazide), which helped control the symptoms to a degree and never made them worse. Others use sulfasalazine, which is an older drug but helpful for some people.
Clearly your body doesn't tolerate mesalamine, and you shouldn't be taking it. Talk this over with your doctor. If he or she isn't willing to try a different drug to help you, consider changing doctors or at least getting a second opinion. There are more options available, and taking something that makes you worse doesn't make sense at all.
Welcome to the forum, by the way.