To      : Lisa Marasco
Re      : Valproic acid, carbamazepine

I would refer you to Nau's paper below concerning valproic acid(1).  In this
paper he reviewed a number of patients.  The average dose varied from 7.7 to 31
mg/kg/day.  Assuming a 70 kg woman, 1000 mg/d would be about 14 mg/kg/day.  So
you can see,  some of the patients reviewed by Nau were receiving much high
doses than your patient.   In this study,  the infants received via breastmilk,
less than 3% of the maternal dose which is not therapeutic.  But the half-life
in infants is very long, and I would suggest occassional blood levels on the
infant, and liver enzymes if the infant breastfeeds just to be safe.   Nau
theorizes that the plasma level in the infant would be 14% of the mothers
levels,  a level that is far lower than the exposure in-utero.

As for carbamazepine,  the oral absorption in the newborn is slow and highly
variable.  I would refer you to Nau(1982).  In a number of women who used
carbamazepine at doses from 400-1000 mg/day,  the breast milk levels were all
less than 3.7 ug/ml.  The maximum reported plasma levels in breastfed infants
have been 0.5-1.8 ug/ml which are subtherapeutic.

Again,  after several weeks of breastfeeding,  the infant's plasma could be
monitored for carb and valproic acid just to be sure.

Regards
Tom Hale, Ph.D.

1.      Nau H, Rating D, Koch S, et.al.  Valproic acid and its metabolites:
placental transfer, neonatal pharmacokinetics, transfer via mother's milk and
clinical status in neonates of epileptic mothers.  J. Pharmacol Exp Ther.
219:768-777,1981.

2.      Nau H, et.al. Anticonvulsants during pregnancy and lactation.  Clin.
Pharmacokinetics 7:508-543,  1982.