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
MGH Psychiatry Academy Expert Online Forum – Women’s Mental Health: Treatment-Emergent Side Effects of Psychiatric Medications in Women: Recognition and Management
Does Lamictal decrease the contraceptive efficacy of the NuvaRing?
Lamictal does not decrease the contraceptive efficacy of the NuvaRing.
However, the NuvaRing and oral contraceptives containing estrogen may decrease Lamictal levels. Thus, if you have a woman who has been stable on a given dose of Lamictal who is starting the NuvaRing or an oral contraceptive, she may need to increase her dosage of Lamictal to maintain the same blood level.
Does Lamictal decrease the contraceptive efficacy of the birth control patch?
I have the birth control patch and it’s been rendered completely ineffective for regulating my periods since starting Trileptal.
This is after over 6 years of the patch with absolutely no problems.