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  • Title: Antiepileptic medication and oral contraceptive interactions: a national survey of neurologists and obstetricians.
    Author: Krauss GL, Brandt J, Campbell M, Plate C, Summerfield M.
    Journal: Neurology; 1996 Jun; 46(6):1534-9. PubMed ID: 8649543.
    Abstract:
    Hepatic enzyme-inducing antiepileptic drugs (AEDs) lower oral contraceptive (OC) sex hormone levels approximately 40% and increase the risk of unplanned pregnancies in women with epilepsy. AEDs also increase the risk of birth defects in offspring of women with epilepsy. We performed a national survey to determine obstetricians' and neurologists' knowledge of OC and AED interactions and the risk of birth defects for women with epilepsy taking AEDs. We received responses to a mailed questionnaire from 160 of 1,000 neurologists (16%) and 147 of 1,000 obstetricians (15%) from 47 states. Practice demographics and ages of responders were typical for U.S. neurologists and obstetricians. Ninety-one percent of neurologists and 75% of obstetricians said they treat women with epilepsy of child-bearing age. Only 4% of the neurologists and none of the obstetricians, however, knew the effects of the six most common AEDs on OCs, even though 27% of neurologists and 21% of obstetricians reported OC failures in their patients taking AEDs. Although increasing OC doses can compensate for insufficient OC sex hormone levels due to AEDs, most physicians do not increase the doses. Even though the risk of birth defects for the offspring of women with epilepsy is 4 to 6%, up from the background level of 2%, 44% of neurologists thought the risk was lower (0 to 3%), and some of the respondents guessed that it was as high as 50%. Many neurologists and obstetricians do not have accurate information to counsel women with epilepsy properly about their contraceptive and pregnancy choices. Responses from 160 of 1000 neurologists (16%) and 147 of 1000 obstetricians (15%), selected from an American Medical Association listing to receive a mailed questionnaire, revealed a disturbing lack of knowledge about the interactions between antiepileptic medications and oral contraceptives (OCs). Hepatic enzyme-inducing antiepileptic drugs lower OC estradiol levels by about 40% and may reduce free progestin levels, thereby increasing the risk of unplanned pregnancy; moreover, antiepileptics increase the risk of birth defects in their epileptic users, who already have a 4-6% increased risk of such defects. Physicians can reduce, but not prevent, the risk of unwanted pregnancy by increasing the OC estradiol dose to at least 50 mcg and prescribing valproic acid and gabapentin (non-enzyme-inducing antiepileptics). 91% of neurologists and 75% of obstetricians reported that they treated epileptic women of childbearing age, and 27% of the former and 21% of the latter physicians acknowledged cases of OC failure in these patients. Only 4% of the neurologists and none of the obstetricians knew the effects of the 6 most common antiepileptic drugs on OCs. Just 41% of neurologists and 43% of obstetricians routinely had patients adjust their OC doses if they were taking antiepileptics. Such adjustment was more likely among physicians who had an epileptic patient with an unintended pregnancy and those who had accurate knowledge of OC-antiepileptic drug interactions. 44% of neurologists and 23% of obstetricians underestimated the birth defects risk as 0-3%. Since the physicians who chose to respond to this survey were presumably more concerned and knowledgeable about the reproductive effects of antiepileptic drugs than those who chose not to respond, continuing education efforts are urged to enable health care providers to counsel epileptic women about contraception.
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