There have been a lot of posts on this topic recently, so I wanted to pass along a book that I discovered. The title is
Medications and Mother's Milk, written by Thomas W. Hale, PhD. Dr. Hale is supposed to be the leading expert on breastfeeding in the U.S.
It is an EXCELLENT book if you are pregnant or are planning to become pregnant and are thinking of breastfeeding. The book is organized by medication, so you can use the index to look up the name of your medication (i.e. Asacol, Rowasa, Remicade, etc.). It's very easy to use. Once you get to the section on your medication, the book gives the complete etimology of breastfeeding while taking that medication. Dr. Hale and his peers have conducted studies with the medications, and they tell you how much of your medicine was secreted via breastmilk, how it affected the baby, etc. The book tells you the risks associated with breastfeeding on that medication, and also gives the pregnancy-risk category.
I am 28 weeks pregnant and was still debating breastfeeding due to the Asacol, Rowasa and Nexium that I use on a daily basis. After reading those sections of Dr. Hale's book and discussing with my high-risk OB and the three pediatricians we interviewed, I will not be breastfeeding. If you have any doubts, you should check out this book and discuss it with your OB and pediatrician.