Contraception and Epilepsy

Women with epilepsy need reliable contraception for two reasons: enzyme-inducing antiseizure medicines reduce the effect of most hormonal methods, and several antiseizure medicines, especially valproate, are teratogenic. Seizure frequency can change in pregnancy, so planned pregnancy is better than unplanned.

Assessment. Seizure type and control, current and planned antiseizure medicines, enzyme-inducing or not, pregnancy plans, mood, bone health, bleeding pattern, and whether the antiseizure medicine is teratogenic.

Enzyme-inducing medicines. Phenytoin, carbamazepine, phenobarbital, primidone, oxcarbazepine and topiramate (at higher doses) induce metabolism and lower contraceptive hormone levels.

Non-inducing medicines. Valproate, levetiracetam, lamotrigine (but oestrogen lowers its level), gabapentin, pregabalin and ethosuximide do not lower hormone levels meaningfully.

Lamotrigine and oestrogen. Ethinylestradiol lowers lamotrigine levels by about half, so combined pills can precipitate seizures; the dose may need to be raised on starting and lowered on the pill-free week or stopping.

Teratogenicity. Valproate carries the highest malformation and neurodevelopmental risk; carbamazepine, phenytoin, phenobarbital and topiramate also carry risk.

Eligibility by method.

Method comparison. Intrauterine devices and DMPA are most reliable with enzyme-inducing therapy. Implants can be used with consistent condoms. Pills are avoided with enzyme inducers.

Bone health. Enzyme-inducing therapy lowers bone density; DMPA adds to the effect, so weigh DMPA in long-term inducer users, assess fractures and vitamin D, and consider other methods.

Emergency contraception. Copper T 380A within 5 days is the best choice with inducers; if oral, levonorgestrel 3 mg single dose within 120 hours; ulipristal is less effective with inducers.

Regimen lines.

• Copper T 380A: insert, up to 12 years; levonorgestrel 52 mg device, 5 years; no backup; not affected by antiseizure medicines.

• DMPA 150 mg intramuscularly every 13 weeks, up to 4 weeks late, or 104 mg subcutaneously every 13 weeks, up to 4 weeks late; backup 7 days if started after day 7 of bleeding.

• Etonogestrel 68 mg rod (3 years) or levonorgestrel two 75 mg rods (5 years or 3 years by system): with enzyme inducers add condoms throughout and for 28 days after stopping the inducer.

• Combined pills: avoid with enzyme inducers and with lamotrigine; if used with non-inducers, ethinylestradiol 30 micrograms with levonorgestrel 150 micrograms daily for 21 days with the usual 7-day break.

• Progestin-only pills: avoid with enzyme inducers.

Preconception. For planned pregnancy, review the antiseizure regimen with the neurologist, switch away from valproate where possible, and give folic acid 5 mg daily before conception and through the first trimester when on valproate or enzyme inducers.

Follow up. Review seizure control, bleeding, side effects and medicines at each antiseizure review; reassess method after any medicine change.

Contraceptive failure. Pregnancy on an enzyme inducer: exclude ectopic pregnancy, review the antiseizure regimen urgently, do not stop medicine abruptly, and refer for specialist antenatal care.

Seizure change with hormones. Seizure worsening after starting or stopping a combined pill with lamotrigine needs a lamotrigine level and dose adjustment.

Bleeding. Manage with ibuprofen 800 mg three times daily for 5 days after excluding pregnancy and pathology; avoid combined pills as a treatment with inducers.

Red flags. New or worsening seizures, missed bleeding, pelvic pain.

Referral and escalation. Refer pregnancy, uncontrolled seizures, and need for a change of antiseizure regimen to a neurologist or obstetrician.