Women with epilepsy who use hormonal birth control may face reduced contraceptive protection because many are also prescribed antiseizure medicines that speed up hormone breakdown, a new analysis shows.
Study reveals extensive prescription overlap
Research published in Neurology found that about 1 in 3 women with epilepsy on hormonal contraception were also taking enzyme-inducing antiseizure drugs. “These were not simply brief or isolated prescription overlaps,” said Dr. Laura Kirkpatrick, an assistant professor at the University of Pittsburgh School of Medicine. “For many people, the overlap continued for months.”
Unintended pregnancies are a particular concern, as pregnancy complications occur more often in people with epilepsy and some seizure medications can harm a developing fetus. “Pregnancy planning is especially important for people with epilepsy, but patients may not realize that some antiseizure medications can interact with some forms of hormonal contraception,” noted Dr. Page Pennell, chair of neurology at the same institution.
The interaction involves enzyme-inducing antiseizure medicines, which accelerate the metabolism of contraceptive hormones. Drugs in this class include carbamazepine, oxcarbazepine, phenobarbital, phenytoin and topiramate.
Investigators examined U.S. Medicaid claims covering nearly 111,000 women of childbearing age diagnosed with epilepsy. Roughly 22,000 of them had prescriptions for both hormonal birth control and an interacting antiseizure medication.
Among those, 33% experienced at least one period of 14 days or more when the two therapies overlapped. The median duration of overlap was about seven months, meaning half of the cases lasted longer and half shorter.
Women with an intellectual disability were more than twice as likely to receive overlapping prescriptions compared with those without such a disability. Higher odds also appeared among patients with drug-resistant epilepsy and those aged 35 or older.
Safer contraceptive options exist
The report emphasizes that not all contraceptives are affected by these drug interactions. Hormonal intrauterine devices and copper IUDs remain fully effective and should be discussed as alternatives. “It is important for people with epilepsy to know that not all forms of contraception are affected by these medication interactions,” Kirkpatrick added.
The authors caution that the study did not measure how many unintended pregnancies actually resulted from the overlaps. “Our study did not look at pregnancy outcomes or determine whether participants experienced contraceptive failure, so more research is needed to better understand the real-world impact of these overlapping prescriptions,” Kirkpatrick said.
For additional information on antiseizure medications and reproductive health, see the Cleveland Clinic resource.