Blood levels of many commonly used antiepileptic drugs drop dramatically with the onset of pregnancy, which can result in ‘breakthrough seizures’ according to a study published in JAMA Neurology.
The findings, collected as part of the multicentre study Maternal Outcomes and Neurodevelopmental Effects of Antiepileptic Drugs (MONEAD), explain why many people with epilepsy start experiencing breakthrough seizures after conception, underscoring the need to increase antiseizure medication doses and closely monitor blood levels over the course of pregnancy.
A fine-tuned medication regime is critical in epilepsy. “Some people mistakenly believe that changes in the drugs’ blood concentration won’t occur until after 20 weeks of pregnancy, but our study shows how important it is to start monitoring and adjusting patients’ medication dosages early on,” said lead author Dr Page Pennelll. “Nearly half of all pregnancies in the United States are unplanned, so it is important to ensure that doctors have a clear picture of each patient’s baseline drug level even if they are not trying to conceive.”
A life-altering neurological condition, two-thirds of epilepsy cases do not have a known cause. In people with epilepsy, nerve cells in the brain are hyper-reactive, causing them to change the pattern of their electrical activity and become spontaneously active. That synchronous activation is manifested in seizures.
Epilepsy has a fraught history of diagnosis and management; people with epilepsy go undiagnosed or under-treated. First-generation drugs to control it had many dangerous side effects and were contraindicated for people who are trying to conceive.
Since then, safer medications have entered the U.S. market and become widely available, but clinicians started noticing a new problem – patients whose epilepsy was successfully managed with medications started having seizures soon after becoming pregnant.
“Identifying which antiseizure medications may have changes in concentrations and at what point in pregnancy those changes occur is important for determining which patients may need to be monitored more closely during pregnancy and after delivery,” said senior author Professor Angela Birnbaum at the University of Minnesota.
To solve the mystery, the researchers embarked on a study to analyse blood concentrations of 10 commonly used antiseizure drugs and compare them across different stages of pregnancy and after childbirth.
The study found that blood levels of seven out of 10 of the medications they examined dropped dramatically — from 29.7% for lacosamide, a commonly prescribed anticonvulsant, and up to 56.4% for lamotrigine.
In addition, the researchers noted that the drop in drug levels occurred mere days after conception.
Source: University of Pittsburgh
