Any time a doctor suggests a new prescription, be sure to talk about what other medicines, supplements, herbs, and vitamins are already being taken. Sometimes one kind of medicine changes the way another kind of medicine works in the body. If two kinds of medicine affect each other, the doctor may prescribe something else or change the amount to be taken.

Because zonisamide is usually used in addition to other seizure medicines, the question of interactions is especially important. Zonisamide has no major effect on other seizure medicines. Some other seizure medicines do affect zonisamide, however, because of their effects on the liver. These medicines increase the metabolism and excretion of zonisamide, so it does not stay in the body as long. Some of the seizure medicines with this effect are phenytoin (Dilantin, Phenytek), phenobarbital, and carbamazepine (Tegretol, Carbatrol). Zonisamide can be used with these medicines, but the dosage will need to be increased.

Other types of medicines also have similar effects on zonisamide. This is why it’s important for you to tell the doctor about all of the prescription and over-the-counter medications that you take, as well as herbs and dietary supplements (St. John’s wort, for example).