Just wnet to the dentist and was given quite a bit of isocaine...can I still nurse? ## The active ingredient in Isocaine is the local anesthetic Mepivicaine. From the information I can find, it is not known whether or not this is excreted in breast milk. Have you tried asking your doctor or the dentist? If you are unsure, it may be advisable to wait at least 24 hours, before going back to breast feeding your baby, just to be on the same side.