Perinatal exposure to maternal lamotrigine: clinical considerations for the mother and child

The question of neonatal safety during breastfeeding when mothers are taking lamotrigine (LTG) has become more prevalent in my practice. There are some theoretical concerns about breastfeeding while taking LTG, which have been compounded by a published case report of toxicity in the breastfed neonate of a mother taking LTG. How should I advise my patients who wish to breastfeed while taking LTG?

Most neonates born to mothers taking LTG have already been exposed to the drug for 9 months in utero, given the chronic indications for which the drug is intended. Lamotrigine exposure via breast milk is considerably less than placental transfer, with serum LTG concentrations in neonates higher at birth than during lactation. While a single case of toxicity has been reported in a neonate exposed to LTG via breast milk, in most circumstances, breastfeeding can be initiated and maintained given the tremendous benefits of mothers' milk. On the other hand, toxicity during breastfeeding might occur more commonly in the mother, if sufficient and gradual dose readjustments are not undertaken in the weeks following delivery.