> Metformin (Biguanide) is another agent that could
>be adequate because it does not cause hypoglycemia.  However, this agent
>could increase the risk of the infant developing lactic acidosis.  There
>is not much information on the newest antidiabetic agent, troglitazone
>(Thiazolidinedione).  This agent could possibly be used safely in the
>breastfeeding woman (Everett, 1997, p. 319-321).

Julie,
I've been researching these two drugs a bit, so I'll share what I know.

Metformin (glucophage) has comparatively low protein binding and is a
small molecule, thus the probability that it will pass into the milk.
There have been no controlled trials of its use on breastfeeding mothers
to date, though other research has followed women on metformin, some of
whom became pregnant during the studies and continued the medication
without apparent ill effect to the fetus.

I am currently following two women, one who is taking metformin during
her pregnancy (due in a couple of months), the other who started on
metformin about 4 mos pp (it took that long for her to gather enough
research and find a doctor willing to examine the info and follow her and
baby) and is having her doctor monitor baby by blood tests.  I find it
interesting that there has been a pediatric concern expressed for
inducing hypoglycemia in an infant, yet with adults it is known that this
particular drug does *not* cause hypoglycemia in the healthy,
non-diabetic adult.  The concerns with lactic acidosis are probably the
most relevant of any concerns, but this problem has been noted mainly in
adults who have compromised renal function. I do not know how we should
categorize the newborn infant's renal maturity relative to the info we
have on adults--- if the lactnet peds would like to comment on this, I'd
be interested in their input.

As for troglitizone (Rezulin), this drug is highly protein bound and has
a large molecular weight, making it unlikely to pass into breastmilk in
significant quantities. The adult concerns for this drug parallel those
for metformin, with the added possibility of some GI upset and/or
problems with decreased red blood cell counts, hematocrit and hemoglobin.
No pediatric concerns are expressed in Hale's book.  Troglitizone appears
very good on paper, and I do believe that there are trials similar to
metformin where women did become pregnant during the studies with no
apparent problems. The one concern I have is some recent reports which I
have yet to review concerning some unusual mortality, though I have also
heard that it relates to people who already had other health problems.

The above mentioned studies can be found on the web--- home page of Dr.
Charles Glueck, while the specific med info can be found in Hale's book.

Lisa Marasco, BA, IBCLC