I think that the antibiotics can also be used if necessary for the
rosacea and breastfeeding continued.  Tetracycline (doxycycline), you
say, surely contraindicated!  Tetracyclines are a beautiful example of
why a drug which is normally contraindicated for a child or baby is not
necessarily contraindicated for the breastfeeding mother.

Why?  Look in the textbooks.  "Do not to give tetracycline with milk",
the reason being that the tetracycline binds to calcium and is thus not
absorbed.  If the mother is taking tetracycline, only small amounts will
appear in her milk, and what little does will be bound to calcium and
not absorbed by the baby.  I suppose there is a theoretical risk of
decreased calcium absorption by the baby but this is pretty minimal and
not likely significant.  If there are new tetracyclines which are not
bound to calcium, then the problem of brown teeth no longer exists.

Jack Newman, MD, FRCPC