Zonisamide, sold under the brand name Zonegran among others, is a medication used to treat the symptoms of epilepsy and Parkinson's disease.

[9] It has been approved for the treatment of the motor symptoms of Parkinson's disease (PD), as an adjunct to levodopa, in a few countries such as Japan.

The precise mechanism by which zonisamide exerts its antiseizure effect is unknown, although it is believed that the drug blocks sodium and T-type calcium channels, which leads to the suppression of neuronal hypersynchronization (that is, seizure-form activity).

[33] Eisai also markets Zonegran in Asia (China, Taiwan, and fourteen others)[34] and Europe (starting in Germany and the United Kingdom).

[36] It has also been studied for obesity[37] with significant positive effects on body weight loss and there are three ongoing clinical trials for this indication.

[41] Zonisamide has been studied for and used as a migraine preventative medication, when topiramate is either ineffective or cannot be continued due to side effects.