Saliva Test May Offer Noninvasive AED Drug Monitoring in Pregnant Women

Caroline Cassels

December 07, 2007

December 7, 2007 — A simple saliva test in pregnant and postpartum women with epilepsy might offer a noninvasive, more practical and convenient method of monitoring serum concentrations of the antiepileptic drug (AED) lamotrigine ( Lamictal, GlaxoSmithKline).

In a small pilot study presented here at the American Epilepsy Society 61st Annual Meeting, investigators at the Cleveland Clinic, in Ohio, demonstrated that maternal salivary concentrations of lamotrigine closely correlated with blood levels throughout pregnancy and up to 3 months postpartum.

"Like many other antiepileptic medications, we know lamotrigine blood levels can change throughout pregnancy and increase a woman's risk of having a breakthrough seizure or toxicity. This warrants careful monitoring, but blood testing is invasive. The results of this study indicate that a quick and simple saliva test may suffice as a noninvasive alternative," study investigator Tanvir Syed, MD, told Medscape Neurology & Neurosurgery.

A recent study by investigators at Emory University School of Medicine, in Atlanta, Georgia, showed that lamotrigine monotherapy is associated with an increase in seizure frequency in up to 75% of pregnancies and that clearance of the drug can increase by 89% in the third trimester, compared with prepregnancy levels ( Neurology. Published online November 28, 2007).

Furthermore, they found that ratio-to-target concentrations of less than 65% were a predictor of seizure worsening, a finding that might inform future treatment guidelines and highlight the need for careful, frequent, AED monitoring.

Stable Relationship

The current study included 11 pregnant women in the first trimester of pregnancy or in the second trimester with a prepregnancy baseline lamotrigine concentration. To qualify for study enrollment, women had to be on a stable dose of lamotrigine for a minimum of 2 weeks before entering the study.

Individuals with significant hematologic or metabolic abnormalities and those with a history of noncompliance were excluded from the study. A total of 8 study subjects had focal epilepsy and 3 had idiopathic generalized epilepsy. All subjects were on lamotrigine for seizure control; however, 3 women were also taking carbamazepine.

Blood and salivary samples were collected during each month of pregnancy, at delivery, at 24-, 48-, and 72-hours postpartum, and then 1 to 2 weeks and 3 months postpartum. Ultimately, time was divided into broad categories: baseline (antepartum), pregnancy trimesters, and postpartum periods.

Generalizable Results?

A total of 105 concurrent serum and salivary samples were obtained. Lamotrigine dose was increased in 9 cases during pregnancy because of fluctuating AED clearance levels.

Despite these fluctuations, the researchers found that there was a stable relation between serum and salivary concentrations during all stages of pregnancy and in the postpartum period.

According to Dr. Syed, it is possible that saliva testing during pregnancy extends beyond lamotrigine to other AEDs. However, he said, this would require additional research.

"The extent to which other AEDs are represented in the saliva vs serum would probably vary between different medications, so each drug would have to be tested in a separate study," he said.

Dr. Syed added that future research will aim to replicate the results of this pilot study in a much larger cohort.

The study was funded by GlaxoSmithKline.

American Epilepsy Society (AES) 61st Annual Meeting: Abstract 3.243. Presented December 3, 2007.

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