Ruth:  For details on Zoloft (sertraline), see the archives for Nov 27,
1995.  Dr. Hale posted on it, mentioning one study which showed very low
levels in human milk, but that study had not looked at active
metabolites.  Although it appears to be the best of the SSRI's since
prozac (fluoxetine) has an extremely long half-life and there have been
some adverse effects reported in infants, and paxil (paroxetine) has no
available data, it is not necessarily the best anti-depressant in
lactating women.  The tricyclics, such as nortriptylene and
amitriptylene, have a longer track record and more data on their relative
safety.  If they can be tolerated, they would probably be best.
As for your question of why medications which are used in pregnancy are
then  "contraindicated" during lactation, this is probably complex.  In many
cases, you are right about the fetus getting more exposure than a
breastfeeding baby.   However, the mechanisms of entry through the
placenta can differ from entry into human milk, so it doesn't always
follow that a drug will get in to milk less than through the placenta.  I
think one reason doctors contraindicate a drug which they would use
during pregnancy is that during pregnancy there is no choice about
exposing the fetus, but during postpartum, there is a choice of using
abm.  Needless to say, most of us would believe that unless the drug
posed serious risk to the baby, the risks of not breastfeeding outweigh
the risk of its use.  However, many physicians still don't believe that.
Alicia.  [log in to unmask]