Contraception for women with epilepsy

Abstract 

The risk of teratogenicity associated with many antiepileptic drugs (AEDs) means that effective contraception is particularly important in this group. Several commonly used AEDs interfere with the combined oral contraceptive pill (COC), either by induction of the hepatic cytochrome P450 enzyme system, or by other mechanisms. They include carbamazepine, oxcarbazepine, phenytoin, phenobarbital, primidone and topiramate. In these patients, use of the COC may still be possible using a combination of pills containing at least 50 µg oestrogen, and by ‘tri-cycling’, though for maximal efficacy it should be combined with a barrier method. The occurrence of break-through bleeding suggests that a higher dose of oestrogen is necessary, although its absence does not guarantee contraceptive efficacy. The progesterone-only pill, progesterone implants and combined contraceptive patches are not recommended for women taking these AEDs. Lamotrigine may also reduce the efficacy of the oral contraceptive pill, and the level of lamotrigine in the blood may be reduced by the introduction of the COC, necessitating an increase in lamotrigine dosage.

Intramuscular medroxyprogesterone is not affected by these AEDs and may be given every 12 weeks, as in other women. Intrauterine devices releasing hormones locally are similarly unaffected. Where emergency contraception is required, an increased dose is necessary in women taking these drugs. Non-hormonal methods of contraception can be used in women with epilepsy as for other women, and hormonal methods of contraception can be used in the usual way by women taking AEDs that do not affect the oral contraceptive pill.

Keywords:  contraception , epilepsy , anti-epileptic drugs

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