There are several reasons why this drug may be okay for nursing mothers.

First of all, it is fairly poorly absorbed from the gastrointestinal
tract (about 14-18% of the total is absorbed).  Secondly, the absorption
is decreased when taken with food (as the baby will take it).  Thirdly,
it is quite highly protein bound.  Fourthly, rather uncommonly, I think,
tacrolimus is present mostly in the red blood cells, which further
decreases the concentration in the plasma, and it is the concentration
in the plasma which influences the milk concentration.

Children seem to require higher dosages to achieve therapeutic blood
levels, but I doubt that these studies were done in neonates.

I don't know if Frank Nice knows any more about this drug.  I have no
knowledge of any studies on milk levels.  I think though, that the
mother should decide on this issue.  Here is a chance to do some
research.

Jack Newman, MD, FRCPC