Yes, it is possible for certain drugs to interact when used in combination
by a mom (a cumulative effect is only one type of interaction that can
occur).  This could also occur with a drug used by the mom and a drug being
taken by the breastfeeding infant.
General guidelines are possible; there are drug interaction tables
available, BUT it is always best to check out each case of combination drugs
to see if an interaction exists and if it does, what is the SPECIFIC
interaction.
Frank J. Nice, DPA, CPHP

             ***********************************************
The LACTNET mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software together with L-Soft's LSMTP(TM)
mailer for lightning fast mail delivery. For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html