BALTIMORE—Women with epilepsy who take hormonal contraception have seizures at greater frequencies than those who take nonhormonal contraception, and the rate is further affected by the type of antiepileptic drug (AED) that they use, researchers reported at the 65th Annual Meeting of the American Epilepsy Society.
In a retrospective study of women with epilepsy between the ages of 18 and 47, 17.8% of women who took hormonal contraception had an increase in seizures. By contrast, 2.9% of patients who took nonhormonal contraception experienced an increase in seizures.
The Epilepsy Birth Control Registry
Kristen M. Fowler, RN, MA, of the Harvard Neuroendocrine Unit of Beth Israel Deaconess Medical Center in Boston, and colleagues conducted the study to determine whether changes in seizure frequency were correlated with hormonal or nonhormonal contraception. The researchers also studied whether changes in seizure frequency were linked to the category of AED that patients used.
The results are based on the first 300 women with epilepsy to respond to the Epilepsy Birth Control Registry, a survey conducted on the Internet. Ms. Fowler and her team used univariate analysis to determine whether the types of contraceptive and antiepileptic therapy interacted with each other or predicted changes in seizure frequency.
AEDs’ Effect on Seizure Frequency
In addition to the type of contraceptive, the researchers found that the type of AED that a patient used affected the frequency of seizures. In women taking hormonal contraception, 21.43% of patients using glucuronidated AEDs experienced increased seizures. Among this group of AEDs, valproate was associated with the greatest seizure exacerbation with hormonal contraception, as 43.6% of women who took valproate had an increase in seizures. In comparison, 7.7% of patients who took valproate and nonhormonal contraception experienced an increased number of seizures.
Other types of AEDs were correlated with lower rates of increased seizures than glucuronidated drugs were. Women who took an enzyme-inducing AED and hormonal contraception experienced an increase in seizures at a rate of 20.39%. In contrast, 6.15% of patients taking a nonenzyme-inducing AED and hormonal contraception experienced increased seizures. For example, 24.4% of women taking carbamazepine, an enzyme-inducing AED, and hormonal contraception experienced more frequent seizures, while 8.9% of women taking carbamazepine and nonhormonal contraception had an increase in seizures.
Seizures increased in 24.4% of women taking hormonal contraception but no AED. Among women who took nonhormonal contraception but no AEDs, 6.7% experienced increased seizures.
No significant relationship existed between a decrease in seizures and the category of AED, according to the study. Seizures decreased in 25% of women who took no AED, 26.3% of women who took an enzyme-inducing AED, 41.7% of women who took a glucuronidated AED, and 44.4% of women who took a nonenzyme-inducing AED.
The researchers concluded that the categories of contraceptive and AED “are significant predictors of changes in seizure frequency and have significant interaction.” Understanding of systemic hormonal contraception’s effect on seizures is limited, however. “Prospective investigations are needed to determine whether these findings represent important seizure safety issues or reporting biases,” noted Ms. Fowler and colleagues.
—Erik Greb