Rifaximin is a fairly new antibiotic that was used successfully in Europe, I believe, for several yrs before getting approval in U.S. the last couple of yrs. It is supposed to be non-systemic, acts locally in the intestines & has been used to treat rectal ulceration. Seems like the gastro is telling your daughter to try it-- another test. However, for her to use Colazal is perfectly sensible; many of us have had better results with it than with older oral 5-ASAs like Asacol. RE blood tests: I don't think that any of us were constantly retested during the 1st few months after diagnosis with UC. The patient should try to recoup nutrients thru diet-- so long as your daughter can eat/drink & lower no. of bms daily she should not be in mortal danger! / Old Hat