SUNDAY, June 5 (HealthDay News) -- Four of the most frequently prescribed epilepsy drugs appear to increase the risk of serious birth defects when taken early in pregnancy, a new study finds.
And the higher the dosage, the greater the risk, the international team of researchers reported in the June 6 online edition of The Lancet Neurology.
"Our results show that dose selection is as crucial as the choice of drug," the authors said in a journal news release. Their study gives doctors the opportunity to prescribe the safest anti-seizure medication at the safest level for women with epilepsy who want to get pregnant, they said.
The drugs studied were carbamazepine (Tegretol, Epitol), lamotrigine (Lamictal), valproic acid (Depakote), and phenobarbital.
The rate of birth defects was higher with increased dose for all the drugs, the researchers said, but they emphasized that the vast majority of women in their study delivered healthy children.
Most women with epilepsy need to take anti-seizure medication or risk harming themselves or their baby. Previous studies found that valproic acid, in particular, might increase the risk of birth defects, but those studies didn't look at individual doses. Nor did they take into account other influential factors, such as family history of birth defects or severity of epilepsy.
"Present guidelines caution on the use of valproic acid during pregnancy, but offer little guidance on alternative options and how to manage women whose seizures cannot be controlled by other drugs," Dr. Torbjorn Tomson, of the Karolinska Institute in Stockholm, Sweden, and colleagues, said in the news release.
For their 11-year study, the researchers used data from the International Registry of Antiepileptic Drugs and Pregnancy on nearly 4,000 pregnancies in 33 countries.
In all, 230 pregnancies resulted in major birth defects by the end of the first year after bi
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