To determine the efficacy, fluctuations in anti-epileptic drugs (AED) level per trimester, tolerability and outcomes in women with epilepsy (WWE) treated with zonisamide (ZNS) during pregnancy.

Among the newer generation of AEDs, the most commonly prescribed AEDs during pregnancy include lamotrigine and levetiracetam. There is insufficient data regarding other AEDs including ZNS.  For routine use of ZNS during pregnancy, information about the efficacy, need for titration and safety is much needed. 

Retrospective chart review of pregnant females aged 18-45 years old who were seen at the Kentucky Neuroscience Institute at the University of Kentucky Epilepsy Clinic. WWE prescribed ZNS during pregnancy between 1/1/2013-5/24/19 were included. We reviewed seizure frequency, analyzed levels by trimester, investigated reported side effects and monitored for congenital malformations reported in children born to these subjects.

Twenty-nine pregnant WWE were evaluated and treated during this time period, of which 7 were prescribed ZNS. Three patients out of 7 had regular levels checked during their pregnancy. All 3 had a drop in zonisamide level of 17-52% between the first and second trimester. One patient was lost to follow up, one patient had a seizure in the first trimester prior to dose increase while the remaining 5 were seizure free throughout pregnancy. The status of 3 of 7 neonates were discoverable, none of which had congenital malformations. Side effects were consistently addressed in 6/7 subjects, all of whom reported no side effects to ZNS.

Although the sample size was small, this study did show some consistent results. Our findings indicate that ZNS levels can decrease during pregnancy and may require dose adjustments. They also suggest that ZNS may be an effective, well tolerated, and safe treatment for pregnant females with epilepsy. Further larger studies are needed to confirm our results.