Pharmacokinetics of zonisamide in perinatal period.

Zonisamide is widely used for intractable epilepsy and the effects of this drug on fetuses and neonates through the mother taking it for epilepsy need to be clarified. We measured the zonisamide concentration in plasma and breast milk using high-performance liquid chromatography to investigate the transfer of zonisamide through the placenta and breast milk, as well as its pharmacokinetics, in two neonates born to epileptic mothers receiving zonisamide. The transfer rates were 92% via the placenta and 41-57% through the breast milk. The first-order kinetics of zonisamide in the two infants was elimination half-lives of 109 and 61h, respectively.