Why would weaning be necessary if the mother is taking niacin, which is
a water soluble vitamin and thus not stored in body tissues?  Even at
large doses, only small amounts would get into the milk.  I don't think
you can overdose of niacin even if you swallowed grams and grams of it.
You can, by the way, die of vitamin D overdose.  Instead of recommending
weaning, here is an opportunity for the physician to do some research.
Why not start the mother on the niacin and measure levels of niacin and
niacinamide in the milk.  I doubt if this has ever been done.

The thallium requires the mother to wean for a week for what reason?  I
am asking because I don't have much info on it.  As far as I know, it is
not radioactive.  Why would the mother have to wean at all?

Jack Newman, MD, FRCPC