Purpose: To prospectively analyse the pharmacokinetics of lamotrigine (LTG) during pregnancy and lactation in a consecutive series of epileptic pregnant women.
Methods: Nine women on LTG-monotherapy were studied during pregnancy, delivery and lactation, until a mean of 3 weeks postpartum. Maternal blood samples were available from all trimesters as well as umbilical cord blood samples of the newborn 24 and/or 48 h postpartum. In 4 cases we additionally determined the LTG-concentration in breast milk.
Results: The median LTG-clearance was elevated by 197% during the first trimester, 236% and 248% during the second and third trimester respectively. A maximum of 264% was reached at delivery. An average LTG-dose increase by 250% had to be undertaken in order to obtain therapeutic serum levels. In puerperium LTG-clearance decreased again to reach the initial concentrations approximately at the third week postpartum. The median LTG-concentration ratio of the umbilical cord blood to maternal serum was 1.01 (range: 0.56-1.42), while the median LTG-concentration ratio of breast milk to maternal serum was 0.59 (range: 0.35-0.86).
Discussion: Our study confirms the therapeutic relevant changes of LTG-clearance during pregnancy and lactation in women on LTG-monotherapy. Since LTG crosses the placenta, a close monitoring of both mother and newborn is indispensable.