To      : Dr. Newman
Re      : Peripheral disposition of Paroxitine

As per your question concerning paroxitine:

You are correct that it could be more of a problem in a pregnant women,  but in
this situation,  at least the maternal metabolism will prevent a high
level(toxic) in both mom and fetus,  as they are to some degree in equilibrium.
As for fentanyl,  this is exactly what is happening,  the mom's plasma is
pumping tons of fentanyl to the infants' plasma,  which then sequesters the
fentanyl in tissue. Upon birth,  the infant is sedated.

However,  postpartum,  where the newborns levels are determined by his/her own
clearance,  it is conceivable for levels to continue to build up and become
even more of a problem,  but generally only for drugs with long half-lives and
poor clearance.  This is probably why we have a number of published papers on
Prozac(fluoxetine) suggesting significant plasma levels in breastfed infants,
because its active metabolite has a half-life of about 240 hours,  and the
infant simply can't get rid of it quick enough.

As for paroxetine(Paxil),  the fact that it has a relative shorter half-life,
and that the concentration in milk is presumably quite low,  the infant can
probably clear enough that long term buildup in the tissue compartments is
probably quite low... which makes this a preferred drug in comparison to
fluoxetine.

Regards
Tom Hale