Antiepileptic drugs: coprescription of proconvulsant drugs and oral contraceptives: a national study of antiepileptic drug prescribing practice.
OBJECTIVE
To determine the frequency of coprescription of antiepileptic drugs (AEDs) and drugs with proconvulsant potential and of coprescription of AEDs and low dose oral contraceptives.


METHODS
Using information from all 294 fully computerised general practices participating in the General Practice Research Database who entered complete data in 1995, persons were identified who had a prescription for an antiepileptic drug and who had a diagnosis of epilepsy or epileptic seizures in their medical records. Other medication was also recorded.


RESULTS
Of women with epilepsy aged 15-45, 16.7% were on the oral contraceptive pill and of 200 on both an enzyme inducing AED and an oral contraceptive, 56% were on formulations with an estrogen content less than 50 microg. This will be associated with increased risk of contraceptive failure and unwanted pregnancy. Over 10% of all AED prescriptions in adults were associated with simultaneous prescription of at least one drug with a potential proconvulsant effect.


CONCLUSIONS
Prescribers should be alert to the possibility of pharmacodynamic and pharmacokinetic interactions between AEDs and other medication. With the aging of the population of people with seizures, and the polypharmacy often associated with old age, the likelihood of adversely interacting drug combinations will increase.
Shorvon
S D
SD
Epilepsy Research Group, Institute of Neurology, Queen Square, London WC1N 3BG, UK.
Tallis
R C
RC
Wallace
H K
HK
D000293:Adolescent; D000328:Adult; D000927:Anticonvulsants / Q000008:administration & dosage* / Q000009:adverse effects; D003267:Contraception; D003276:Contraceptives, Oral / Q000008:administration & dosage / Q000009:adverse effects*; D003292:Convulsants / Q000008:administration & dosage* / Q000009:adverse effects; D004347:Drug Interactions; D011307:Drug Prescriptions; D004359:Drug Therapy, Combination; D004827:Epilepsy / Q000188:drug therapy*; D005260:Female; D006801:Humans; D008875:Middle Aged; D011247:Pregnancy
D000927:Anticonvulsants; D003276:Contraceptives, Oral; D003292:Convulsants