I would like to support and reiterate the comments of K. West and Dr. Newman
concerning the use of "contraindicated" drugs.

I absolutely cringe when someone asks me for a list of "safe" drugs, and a list
of "Contraindicated" drugs.  Each breastfeeding case must be individually
evaluated for its own merits.  In some cases, using any drug may be dangerous,
 in others, most drugs may be quite safe.

So I generally recommend that people first evaluate the mother-infant
situation prior to using a medication before a decision is made one way or the
other.

As for lithium,  there are few reports that really suggest side effects in
breastfed infants, but instead ocassional offhand comments by the authors (and
AAP) that "this product should not be used in a breastfeeding mother".  As Dr.
Newman suggested,  close evaluation of the infant (lithium plasma levels), is
easily accomplished, and often illustrates that the actual plasma levels in the
infant are quite small and most often subclinical.  I have personally been
consulted on a number of these situations, and the physicians reported to me
that the lithium levels were quite low in the infant(about 25% of moms').

We have the same problem with using thyroxine,  and numerous anticonvulsant
drugs (particularly phenobarbital), many of which have suffered derogatory
comments by certain authors.  My suggestion is that if you need to use a
medication that is "monitorable" by a clinical laboratory test,  then do so.
This way the clinician can feel comfortable about using the medication, and you
can prove a point that the infants plasma levels are generally subclinical.

Regards
Tom Hale Ph.D.