MAJOR — Use With Caution
FDA-documented interaction. Same mechanism as carbamazepine. Contraceptive failure risk is significant.
Evidence level: STRONG
Phenytoin (Dilantin) speeds up the breakdown of birth control hormones, which can make your birth control pills fail. Additional contraception is needed.
Phenytoin induces CYP3A4, increasing metabolism of contraceptive hormones. Can cause contraceptive failure. FDA labels warn about this interaction.
Use additional non-hormonal contraception while on phenytoin. Discuss long-acting contraceptive options with your doctor.
Take Phenytoin at exactly the same times each day — consistency is critical for seizure control. Combined Oral Contraceptives follows its prescribed schedule. Antiepileptics are potent enzyme inducers that can change how your body processes many other medications.
Sole reliance on hormonal contraception
Breakthrough bleeding, spotting, missed periods (possible pregnancy)
Discuss copper IUD or other non-hormonal methods. Higher-dose oral contraceptives may not be reliable enough.
Antiepileptic drug levels are sensitive to enzyme inducers and inhibitors. Discuss any changes with your neurologist before adding new substances. Safer supplement options: magnesium, omega-3s, and B vitamins are generally well-tolerated alongside seizure medications.
Phenytoin (Dilantin) speeds up the breakdown of birth control hormones, which can make your birth control pills fail. Additional contraception is needed.
Take Phenytoin at exactly the same times each day — consistency is critical for seizure control. Combined Oral Contraceptives follows its prescribed schedule. Antiepileptics are potent enzyme inducers that can change how your body processes many other medications.
Breakthrough bleeding, spotting, missed periods (possible pregnancy)
Antiepileptic drug levels are sensitive to enzyme inducers and inhibitors. Discuss any changes with your neurologist before adding new substances. Safer supplement options: magnesium, omega-3s, and B vitamins are generally well-tolerated alongside seizure medications.
Discuss copper IUD or other non-hormonal methods. Higher-dose oral contraceptives may not be reliable enough.
Or browse the full interaction database (121,000+ pairs).