When I was breastfeeding, my GI doctors didn't have any information about what medications were safe for breastfeeding. This database is very useful, and contains all the standard Crohn's medications. I wish I had this resource back then:
"Drugs and Lactation Database (LactMed) - A peer-reviewed and fully referenced database of drugs to which breastfeeding mothers may be exposed. Among the data included are maternal and infant levels of drugs, possible effects on breastfed infants and on lactation, and alternate drugs to consider."
http://www.toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT
"Drugs and Lactation Database (LactMed) - A peer-reviewed and fully referenced database of drugs to which breastfeeding mothers may be exposed. Among the data included are maternal and infant levels of drugs, possible effects on breastfed infants and on lactation, and alternate drugs to consider."
http://www.toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT