Blood levels of some epilepsy medicines lower in pregnancy

Published: March 01 2022
Last updated: May 12 2023

The amount of some epilepsy medicines in the blood drops in women during pregnancy, according to a new study in JAMA Neurology.

The Maternal Outcomes and Neurodevelopmental Effects of Antiepileptic Drugs (MONEAD) study, by Page Pennell and her colleagues, investigated the pregnancy-associated changes in several epilepsy medicines. These were lamotrigine, levetiracetam, lacosamide, oxcarbazepine, zonisamide, carbamazepine and topiramate.

Reduced levels of epilepsy medicines in the blood during pregnancy can lead to more frequent or severe seizures which could be harmful to the woman and baby.

The research included 430 participants – 326 pregnant women with epilepsy (the study group) and 104 women with epilepsy who were not pregnant for comparison (known as controls) – aged 14-45 years. The pregnant women were at less than 20 weeks of pregnancy when the study started. The study group was monitored for nine months after giving birth, with a similar timeframe used for the control group.

In the study group, blood tests were done four times during pregnancy and three times after the women had given birth. Seven blood tests were also done in the control group over 18 months.

Amounts of epilepsy medicines in the blood were compared during and after pregnancy in the study group, and between the study and control groups.

When comparing the blood levels during and after pregnancy in the pregnant women group, levels of many of the epilepsy medicines were significantly reduced during pregnancy. Lamotrigine levels decreased by over a half (56.1%) and levetiracetam by over a third (36.8%). Oxcarbazepine reduced by around a third (32.6%), as did zonisamide (29.8%), and lacosamide levels dropped by two-fifths (39.9%). The authors say that monitoring of medicine levels in the blood should start early in pregnancy, and that increasing the doses of some epilepsy medicines may be needed throughout pregnancy.

There is more information about epilepsy, medicines and pregnancy on the Epilepsy Action website.

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