Which antiepileptic drug is most likely to lead to contraceptive failure when used with oral contraceptives?

Topiramate is an antiepileptic drug that has been shown to significantly impact the effectiveness of oral contraceptives. This occurs primarily through its enzyme-inducing effects, which can accelerate the metabolism of estrogen and progestin in oral contraceptives, thereby reducing their blood concentrations and effectiveness in preventing pregnancy.

Research demonstrates that women taking topiramate should be advised to consider alternative or additional forms of contraception to avoid the risk of contraceptive failure. While all listed antiepileptic drugs can interact with hormonal contraceptives, topiramate carries a higher risk of reducing their efficacy compared to others.

In contrast, valproate, lamotrigine, and phenytoin interact with hormonal contraceptives differently, with some having less severe effects on contraceptive efficacy. For example, while phenytoin is also known to induce liver enzymes that can affect hormonal levels, the magnitude of interaction is typically not as pronounced as with topiramate. Lamotrigine's interaction is less significant, and valproate does not typically affect hormonal contraceptive metabolism to a degree that would commonly lead to failure. Therefore, recognizing topiramate's specific potential for causing contraceptive failure is critical for those managing patients who may