I have UC. I am currently taking Zithromax to treat a sinus infection. This is day 4 and just started having diarrhea which is a side effect of Zithromax. I take Pentasa daily to treat the UC, and my doctor also prescribes Entocort in case of a flareup. Since this flareup seems to be from antibiotics, I am wondering if I should start the Entocort or wait for the antibiotic to run its course.