After a Google search for Trileptal I found out what the generic name is,
oxcarbazepine.
According to the manufacturer only 40% of the drug is protein-bound in the
blood.  For reference, phenytoin is 90% protein-bound and carbamazepine
(sold as Tegretol) 70-80%.
Protein binding is a quick and dirty way of getting a ballpark idea of how
much drug is available to pass into breastmilk.  The lower the degree of
protein binding, the more drug gets into the milk.  It isn't the whole
picture, because the pH and the fat or water solubility will also play a
role, as will the potential toxicity of the drug.

The same website states that both oxcarbazepine and the active metabolite
responsible for its therapeutic effect, are found in breastmilk in
concentrations half that of the maternal plasma.  This sounds high to me,
but I am not an expert on this topic.
By calculating approx. daily milk intake volume, and knowing the plasma
concentration in the mother, one could calculate an approximate daily dose
to the child.  That would give the pediatrician/neurologist couple something
to have fun with after dinner one night, perhaps.

It sounds as though this mother's epilepsy is not easy to treat.  If she
shouldn't be driving, how safe is it for her to be caring for her baby?  The
risks of inadequate control of the epilepsy need to count for something in
the equation too.  This isn't a simple situation by any means.

Rachel Myr
a big time Google fan in Norway

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