Importance of monotherapy in women across the reproductive cycle.

Special treatment considerations are warranted in women with epilepsy, particularly those of childbearing age. Treatment guidelines generally recommend the use of antiepileptic drug (AED) monotherapy at the lowest dose possible during pregnancy. The UK Epilepsy and Pregnancy Register reported that the risk for major congenital malformations is higher with AED polytherapy than with monotherapy (6.0% vs 3.7%, respectively) and that valproate carries the highest individual risk. The AEDs that induce hepatic cytochrome CYP450 enzymes carry particular concern both before and after pregnancy. Hepatic enzyme inducers alter steroid metabolism in women receiving oral contraceptives, increase the risk for contraceptive failure, and interfere with calcium absorption and vitamin D metabolism, thus increasing the risk for osteoporosis and fractures. Vitamin K deficiency is another potential consequence of treatment with a hepatic enzyme-inducing AED, increasing the risk for coagulopathy and neonatal intraparenchymal and intracerebral hemorrhage during the first 24 hours of life. Supplemental vitamin K therapy during the last month of pregnancy is warranted. Preconceptional and gestational folate supplementation may also be warranted to prevent neural tube malformation related to AED treatment. Because AED pharmacokinetics may be altered during pregnancy, plasma AED concentrations should be measured before conception and monthly during pregnancy to prevent seizure breakthrough.