Is there a change in treatment of epilepsy during pregnancy?
Because all anticonvulsants have some potential to be teratogenic or harmful to the fetus, treatment should be aimed toward monotherapy at the lowest functionally effective dose.
Due to physiologic changes that occur in pregnancy the pharmacokinetics of anticonvulsants are usually altered.
Effective prepregnancy anticonvulsant levels should be used as the target levels during pregnancy.
Drug levels should be measured as soon as pregnancy is diagnosed because blood concentrations of anticonvulsants may drop precipitously during the first trimester, as a result of alterations in drug absorption, metabolism, or protein binding.
This is especially true for phenytoin, with its nonlinear kinetics, in which doses may need to be increased by 50% to 100% during pregnancy to maintain prepregnancy levels.
Routine drug levels should be measured each trimester and more frequently if either seizure control worsens or if patients have a history of previous alterations in drug levels during pregnancy.
Because drug clearance returns to prepregnancy norms within 3 to 6 weeks postpartum, prepregnancy anticonvulsant doses should be gradually introduced during this period.
All patients of childbearing age should take folic acid to lower risks of neural tube defects, which have a higher incidence in children born to women taking anticonvulsants.
Women of childbearing potential on anticonvulsants should be on folic acid even prior to conception, and doses up to 4 mg should be prescribed as soon as pregnancy is suspected.