Potential birth control–drug interactions common among patients with epilepsy

Clinical takeaway: Review contraception choices when prescribing enzyme-inducing antiseizure medications for patients with epilepsy who may become pregnant. In this Medicaid analysis, nearly one-third of patients using susceptible hormonal contraceptives had prolonged overlapping exposure to antiseizure medications known to lower contraceptive hormone levels.

Pregnancy planning is especially important for people with epilepsy because unplanned pregnancy has been linked to increased maternal and fetal health risks, and some antiseizure medications (ASMs) have been associated with adverse fetal outcomes. Identifying potentially interacting medication combinations may help support informed contraceptive counseling and shared decision-making.

A retrospective analysis of US Medicaid claims evaluated 21,923 people with epilepsy who were prescribed hormonal contraceptives susceptible to interactions with enzyme-inducing ASMs. Contraceptive methods included combined oral contraceptives, progestin-only pills, patches, vaginal rings, and subdermal implants. Researchers assessed overlapping use with enzyme-inducing ASMs, including carbamazepine, oxcarbazepine, phenytoin, phenobarbital, and topiramate.

Overall, 7,154 patients (32.6%) experienced at least one period of 14 days or longer during which a susceptible hormonal contraceptive overlapped with an enzyme-inducing ASM. On average, the overlap lasted about seven months. More than 60% of overlapping exposures occurred when an enzyme-inducing ASM was added after contraceptive initiation, suggesting opportunities to identify and address potential interactions during treatment changes.

The study did not evaluate pregnancy outcomes or contraceptive failure, and prescription claims data cannot confirm whether medications were taken as prescribed. Even so, the findings suggest that potentially clinically important contraceptive-drug interactions remain common among Medicaid beneficiaries with epilepsy.

"It is important for people with epilepsy to know that not all forms of contraception are affected by these medication interactions," said study author Laura Kirkpatrick, MD, of the University of Pittsburgh School of Medicine. "With informed counseling, people can choose a contraceptive method that aligns with their preferences and health needs."

Source: Harrison E, et al. (2026 Oct 7) Neurology. Contraceptive and Enzyme-Inducing Antiseizure Medication Coprescription Among US Medicaid Beneficiaries With Epilepsy