Teratogenic medications and concurrent contraceptive use in women of childbearing ability with epilepsy.

BACKGROUND

Many antiepileptic drugs (AEDs) have the potential to cause teratogenicity. We evaluated eight antiepileptic drugs (AEDs) classified as Federal Drug Administration (FDA) pregnancy category D, X, or N designations and having documented teratogenic effects. These include carbamazepine, ethosuximide, fosphenytoin, phenobarbital, phenytoin, primidone, topiramate, and valproate. Women with epilepsy (WWE) may need one or more of these AEDs for seizure control but may be unaware of the potential teratogenicity associated with their use. In utero exposure to AEDs increases the risks for both congenital malformations and other teratogenic defects. Given that approximately 50% of pregnancies are unintended, it is likely that women with epilepsy taking these medications could unknowingly put a growing fetus at risk. For women using contraception while taking these medications, many choose combined hormonal contraceptives (CHCs). Drug-drug interactions exist between AEDs and CHCs that may decrease contraceptive efficacy. The aim of this study was to evaluate prescribing patterns for potentially teratogenic AEDs and contraceptive use in WWE of childbearing ability, including those with potential drug-drug interactions. This study also determined the number of WWE of childbearing ability prescribed potentially teratogenic AEDs and documentation of a pregnancy or contraception plan.

METHODS

This was a retrospective, observational study of WWE age 15-44 years, of childbearing ability, prescribed an AED from July 1, 2011 to June 30, 2012, and who had an appointment at the University of Colorado Hospital Outpatient Neurology Clinic (Anschutz Medical Campus).

RESULTS

One hundred fifteen women with an average age of 30.7 years and various types of seizures were evaluated. The majority of patients were prescribed topiramate (34/115, 30%) or carbamazepine (27/115, 23%). Of the women, 30/115 (26%) had a documented contraception method when taking a potentially teratogenic AED. Of these women prescribed contraception, most (18/30, 60%) used an oral combined hormonal contraceptive or progestin-only pill, a majority of which had a potential for a drug-drug interaction with their AEDs (16/18, 89%). Less than 7% of women received counseling on a contraception plan, and 18% of subjects received counseling on a pregnancy plan.

CONCLUSIONS

Most WWE of childbearing ability taking potentially teratogenic AEDs were not using contraception. Those using contraception frequently had a method that has a significant drug-drug interaction which reduces the effectiveness of contraception. Women with epilepsy of childbearing ability prescribed an AED should be using effective contraception or participating in active discussions about pregnancy planning to avoid unplanned pregnancies and possible teratogenic effects of these AEDs. Documentation about pregnancy planning or contraceptive use in WWE of childbearing ability is minimal and should be discussed at least annually. It is critical for providers to discuss with WWE of childbearing ability the benefits and risks of various AED treatments; the need to select appropriate, effective contraception when pregnancy is not desired; and the importance of counseling regarding contraceptive or pregnancy planning.