The fact that the mother is producing less milk does not result in more drug
concentrated in the milk.  The concentration usually will be more or less
the same, though it is possible that "weaning milk" might have a lot more
sodium than regular milk.  This might actually decrease the concentration in
the milk of most drugs, but I'll bet no one has ever studied this.  There is
something for someone to study.

Jack Newman, MD, FRCPC