Anticonvulsants are likely to interact with many other medications. In some cases, the anticonvulsant affects the action of the other medication, and in others, the action of the anticonvulsant is affected. Patients should consult their physicians before taking any additional prescriptions, over-the-counter medications, nutritional supplements or herbal medications.

In general, anticonvulsants add to the effects of alcohol and other central nervous system (CNS) depressants and increase drowsiness. Some other negative drug interactions depend on the type of anticonvulsants being taken.

For example, anticonvulsants such as carbamazepine and oxcarbazepine may reduce the effectiveness of many medications, including oral contraceptives (birth control pills). This makes it necessary for women of child-bearing age to use other forms of birth control when taking certain anticonvulsants.

Divalproex may increase the effectiveness of many medications, including anticoagulants and other mood stabilizers. Certain antibiotics may increase the levels of some anticonvulsants, resulting in a potentially toxic combination.