Contraception for Women with Epilepsy

Additional research is needed regarding effective contraception for women with epilepsy. All commonly used birth control methods, including hormonal contraceptives, barrier devices or substances, and timing techniques, can be used by women with epilepsy. Of these, hormonal contraception is usually the most effective method for preventing pregnancy, but the choice of contraceptive medication can be influenced by the type of seizures and the type of anti-epileptic drugs (AEDs) used. The effectiveness of hormonal contraceptives may be compromised in women with epilepsy who are taking certain AEDs, resulting in unplanned pregnancies. Some women with epilepsy may choose alternative methods of contraception in addition to the hormonal contraceptives.

Hormonal Contraception and Seizures

Current research does not show significant changes in seizure frequency in women with epilepsy who are using hormonal contraceptives. However, anecdotal reports suggest a correlation between this type of contraceptive and changes in seizure patterns. For example, some women with epilepsy may have more seizures, some may have less.

Hormonal Contraception and Antiepileptic Medications

Forms of hormonal contraception include oral contraceptive pills, impregnated intrauterine devices (progestasert), intramuscular hormonal preparations (medroxyprogesterone) and subdermal implantations (levonorgestrel). Hormonal contraceptives do not reduce the efficacy of antiepileptic drugs (AEDs), but there is increased risk for women with epilepsy that any hormone-dependent contraceptive system will fail, due to enhanced binding and metabolism of the steroid hormones (estrogen and progesterone).

• Metabolism of contraceptive hormones by the hepatic cytochrome P450 enzyme system (cyP450) is enhanced by some AEDs: carbamazepine, oxcarbazepine, phenytoin, barbiturates (phenobarbital, mephobarbital and primidone), and topiramate. Valproate and felbamate inhibit the cyP450 system, resulting in no change or even increased levels of exogenous steroids. Gabapentin, lamotrigine, levetiracetam and tiagabine have no effect on this enzyme system and do not interfere with the effectiveness of hormonal contraception.
• Oral contraceptives used by women with epilepsy taking cyP450-inducing AEDs may need to contain higher amounts of estrogen, although even with higher doses, unplanned pregnancies may occur. The commonly used low-dose combined oral contraceptive pill contains <35 mg and this may not be sufficient to prevent ovulation.
• Intramuscular medroxyprogesterone (DepoProvera) is usually given as 150 mg every 12 weeks. Women with epilepsy taking cyP450-inducing AEDs may need the dosage interval of this contraceptive decreased to every 6 to 8 weeks. This form of hormonal contraceptive for women with epilepsy may have undesirable side effects including mood changes. On the other hand, it may also lessen seizures in women with partial seizures, probably by suppressing menstruation.
• The reliability of subdermal levonorgestrel (Norplant), a slow release contraceptive containing progesterone only, may be compromised by AEDs affecting the cyP450 system.

Therapeutic Interventions

• If women with epilepsy use a cyP450-inducing AED (carbamazepine, oxcarbazepine, phenytoin, barbiturates or topiramate), select a contraceptive agent that contains high hormone dosages (adequate to suppress ovulation) and use a barrier method of contraception in addition.
• Mid-cycle spotting or bleeding may signify ovulation, and the addition of barrier methods of contraception will be necessary for protection. Contraceptive failure may occur without mid-cycle spotting.
• Consider double barrier methods or an intrauterine device (IUD) for women with epilepsy.
• Monitor seizure control closely in women with epilepsy using hormonal contraceptives, and emphasize prompt report of altered seizure patterns so that contraceptive methods and/or AEDs can be re-evaluated.

CONTACT

For additional information, contact the Women and Epilepsy Initiative of the Epilepsy Foundation at (800) 332-4050.

REFERENCES

Guberman A. Hormonal contraception and epilepsy. Neurology. 1999;53(Suppl 1):38-40.

Krauss GL, Brandt J, Campbell M, Plate C, Summerfield M. Antiepileptic medication and oral contraceptive interactions: a national survey of neurologists and obstetricians. Neurology. 1996;46:1534-1539.

Mattson R, Cramer J, Darney P, Naftolin F. Use of oral contraceptives by women with epilepsy. JAMA. 1986;256(2):238-240.

Wilbur K, Ensom MHH. Pharmacokinetic drug interactions between oral contraceptives and second-generation anticonvulsants. Clinical Pharmacokinetics. 2000;38(4):355-365.

Practice parameter: Management issues for women with epilepsy (summary statement). Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 1998;51:944-8.