Some antiepileptic drugs can reduce the effectiveness of the contraceptive pill, ‘morning after’ pill and contraceptive implants. These anti epileptic drugs, known as ‘enzyme inducers’, include carbamazepine, oxcarbazepine, phenobarbitone, phenytoin, primidone and topiramate.
They cause the contraceptive hormones to be removed more quickly from the body. For this reason, girls taking these drugs are usually given contraceptive pills with a higher level of oestrogen and advised about other methods of contraception. This should be discussed with a family planning doctor.
Some antiepileptic drugs can affect foetal development, so changes may be made to medication and doses prior to a pregnancy. For this reason pregnancies should be planned well in advance and monitored from an early stage. It is important that all teenagers are given information about the effects of AEDs on contraception and pregnancy before they become sexually active.