http://neonatal.ttuhsc.edu/cgi-bin/discus/discus.cgi?pg=topics&access=guest
This link will take you to Dr. Thomas Hale's website. He's consider the leading expert in meds & mother's milk in the U.S. You can look up your meds here and see if they are safe. Pentasa is safe, but in high doses can cause diarrhea in baby. I have taken asacol (very similar to pentasa) while breastfeeding all 3 of my children and not one of them had any problems.