The interaction between specific birth control preparations and anti-epileptic medications should always be taken into consideration when developing a treatment approach, as taking the two simultaneously may decrease the birth control pill’s effectiveness.
An oral contraceptive (OC) is effective because it delivers high doses of estrogen to prevent ovulation. Unfortunately, some anti-epileptic medications alter the metabolism of birth control pills because they induce a liver enzyme which metabolizes the estrogen contained within the OC. Thus, if a woman is given an anti-epileptic medication along with a birth control pill, her dose of estrogen may be decreased and the OC may cease to be effective.
The main anti-epileptic medications which have this interaction are:
– Carbamazepine (Tegretol)
– Oxcarbazepine (Trileptal)
– Topiramate (Topamax)
– Felbamate (Felbatol)
– Phenytoin (Dilantin)
– Primidone (Mysoline)
This interaction occurs primarily with oral contraceptive pills, but can also occur with the NuvaRing, a vaginal contraceptive ring, because the hormones contained in these preparations are metabolized by the liver.
The birth control patch, on the other hand, is not substantially metabolized by the liver, so the patch and/or barrier methods (such as male or female condoms) may be good options for women who are taking one of the above anti-epileptic medications and are trying to avoid this drug-drug interaction.
Hadine Joffe, MD, MSc