What should I know about birth control and epilepsy?
There are many different types of birth control (also called contraceptives) that are usually taken by mouth. These are often called oral contraceptives or OC. The most common form are called combination pills beause they include forms of estrogen and progesterone. There are also forms of OC that only involve progesterone. Some hormonal contraceptives can be given in other ways and last longer (for example a patch, an injection or shot, an implant placed under the skin, an IUD, or a vaginal ring).
Oral hormonal contraceptives (OC) can be very effective at preventing pregnancy in women taking antiepileptic drugs (AEDs). However, there are two important points:
- AEDs that increase the ability of the liver to break down OCs, such as phenobarbital, carbamazepine [Tegretol, Carbatrol], phenytoin [Dilantin, Phenytek], felbamate [Felbatol], topiramate [Topamax], oxcarbazepine [Trileptal], and perampanel (Fycompa) can increase the risk for OC failure, leading to an unintended pregnancy.
- Although lamotrigine [Lamictal] does not affect OCs, the level of lamotrigine can be lowered by OCs which could lead to breakthrough seizures and a change in side effects.
OCs prevent pregnancy because they contain versions of the hormones estrogen and progesterone. OCs generally prevent pregnancy in the following ways:
- The estrogen component prevents ovulation.
- The progesterone component - produces thick cervical mucus that interferes with sperm movement; may affect the sperm's ability to fertilize the egg; and changes the lining of the uterus so it's hard for a fertilized egg to implant.
It is not known whether the estrogen or progesterone components are more important in preventing pregnancy. Certain AEDs can affect either or both components because of their effects on the liver. For example, felbamate reduces the progesterone component, whereas topiramate reduces the estrogen component. It appears that lamotrigine reduces a type of progesterone called levonorgestrel.
For the best pregnancy prevention, women taking one of these “enzyme-inducing AEDs” (phenobarbital, carbamazepine, phenytoin, felbamate, topiramate, oxcarbazepine, perampanel) should consider:
- Use OCs containing at least 50 micrograms of ethinyl estradiol.
- Avoid low-dose formulations in general.
- If depomedroxyprogesterone acetate injections (Depo-Provera) are used, they should be given more frequently (such as every 10 weeks rather than the usual 12 weeks).
- Use barrier methods of contraception with OCs.
- Consider long-acting forms of contraception, for example IUDs, the patch, injections or an implant. The use of long
Other AEDs that are called “non-enzyme-inducing AEDs” do not interact with OCs. These include valproic acid [Depakote], gabapentin [Neurontin], levetiracetam [Keppra], tiagabine [Gabitril], vigabatrin [Sabril], zonisamide [Zonegran], and pregabalin [Lyrica]. Therefore there are no concerns regarding the treatment of seizures or increased pregnancy risk with these particular AEDs when used alone or in combination with each other.
A special situation occurs with lamotrigine. Lamotrigine blood levels are reduced by 50% when hormonal oral contraceptives are also used.
- Women with epilepsy taking lamotrigine need to be monitored carefully for seizures when OCs are started.
- They should also be checked for toxicity or dose-related side effects when OCs are stopped.
- This monitoring will likely require blood levels to be checked during certain times of the month and before or after a hormonal contraceptive is used.
- To maintain seizure control and avoid side effects, dose adjustments may be necessary. Lamotrigine toxicity may occur with the placebo or pill-free week of the OC regimen.
With these important cautions, OCs can provide excellent pregnancy prevention for women taking AEDs with minimal risk of increased seizures.