This medication seems relative benign if you read Hale's information
about it.  Once again, I feel that there is more to deciding about
drugs and breastfeeding than, "will the baby get some".  The risks of
not breastfeeding are important to factor in, and this seems rarely to
be done.  I would encourage the mother to breastfeed.  Maybe the
clinical pharmacology department of the hospital or university would
measure drug levels in the milk so that this information can be used
for the next mother.

By the way vancomycin is *not* a contraindication to breastfeeding. It
is not absorbed orally, and thus the baby will only get a small amount
into his gut which he will promptly poop out.  "But can't this change
the baby's gut flora?".  Yes, it can.  But so does formula.  Why is it
okay to change the baby's gut flora with formula but not antibiotics,
especially given the risks of formula feeding?

Jack Newman, MD, FRCPC