Of course, there is more information on tricyclic antidepressants and
breastfeeding since my article was published in 1990, but none of the
information currently available or what I have seen in my practice has
changed my recommendation that, with proper monitoring, that tricyclic
antidepressants are compatible with breastfeeding, especially for agents
such as nortriptyline (Pamelor) at doses up to 125mg/day or desipramine
(Norpramin) at doses up to 30mg/day.

Regarding diazepam, diazepam and its metabolite enter milk and may
accumulate in infants, even at low doses.  Its use is not recommended;
if used, infant must be closely monitored (lethargy, sucking problems,
withdrawal symptoms).  Whether to use it or not would be based on the
indication for the mother.  If for a mother in status, why not use it
and continue breastfeeding.  If used for other reasons, other
benzodiazepines could be substituted.  In general, a single dose or
repeated low doses of benzodiazepines are unlikely to produce adverse
effects on health infants; prolonged, high dose treatment should be
avoided.

Hope this is of some help to the nursing students who asked for opinions
Frank J. Nice, DPA, CPHP