Abstracts

Rationale: Family planning is a critical concern for women living with epilepsy (WWE). Choosing an appropriate form of contraception, however, is difficult for WWE as many anti-epileptic drugs have significant interactions with widely used forms of contraception. It is essential that healthcare providers are keenly aware of these interactions. Our aim was to assess residents' understanding of the interactions of hormonal contraception and antiepileptic medications. Previous studies have shown that physician knowledge of these drug-drug interactions, specifically the effect of enzyme-inducing AEDs (EI-AEDs) on oral contraceptive pills (OCPs), is poor (Morrell, et. al, J Womens Health Gend Based Med. 2000; 9: 959-65; Summerfield, et.al, Neurology. 1996; 46: 1534-9). Prior studies did not address the interactions EI-AEDs on other forms of contraception or the interactions of hormonal contraception with lamotrigine. Lamotrigine is becoming one of the most frequently prescribed medications for women of childbearing age and has unique interactions with synthetic hormones. Synthetic estrogens can significantly lower lamotrigine levels, increasing a patient's risk for seizures (Sidhu, et, al, Br J Clin Pharmacol. 2006; 61: 191-9). We hypothesized that residents would be aware of the interactions of EI-AEDs and OCPs, but they would not be aware of other important interactions. Methods: A survey of drug-drug interactions was developed and distributed to all twenty-two neurology residents and forty-four obstetrics and gynecology residents at our institution. For each potential interaction, respondents could indicate "yes," "no" or "I don't know." It was distributed as a paper and an online survey. Results: Nineteen neurology residents and twenty obstetrics and gynecology residents responded to the survey. Most, but not all, respondents knew that enzyme inducing antiepileptic medications, specifically carbamazepine (76.9%), phenytoin (71.8%), and oxcarbazepine (59%) affect the efficacy of combined OCPs, but did not know that carbamazepine would affect the efficacy of etonogesterel implant, depot medroxyprogesterone and the contraceptive vaginal ring. Most respondents did know that levetiracetam does not have significant interactions with most forms of birth control. When asked which AEDs would be affected by estrogen containing OCPs, 46.2% indicated lamotrigine would be affected, but a similar percentage indicated the same for carbamazepine and phenytoin, suggesting they are not aware of the specific interaction. Conclusions: Resident knowledge of interactions between EI-AED and OCPs is relatively high. Awareness regarding other important interactions between AEDs and hormonal contraception, however, is quite low. Further education through the development of guidelines and educational materials is needed and recommended during residency training.