Zonisamide in combination with another antiepileptic drug can reduce seizures, but with some adverse effects.
A third of people with epilepsy become resistant to antiepileptic drugs. Older drugs do not prevent seizures for everyone and they have adverse effects. New drugs have been developed as "add-on" treatments to try and improve this. Zonisamide is one of these. The review of trials found that zonisamide significantly reduced seizure frequency for people with drug-resistant partial epilepsy if zonisamide is added to their usual treatment. There is also an increase in adverse effects, and more research is needed.