Zonisamide for Epilepsy

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Zonisamide for Epilepsy


Generic NameBrand Name

Zonisamide comes in capsule form.

How It Works

It is not clear how zonisamide prevents epileptic seizures.

Why It Is Used

Zonisamide is used to treat partial seizures. It is used most often with other antiepileptic medicines.

How Well It Works

When added to treatment with other antiepileptic medicines, zonisamide can reduce partial seizures in adults.1

Zonisamide may also help reduce absence seizures, myoclonic seizures, and infantile spasms.1

Side Effects

The most common side effects of zonisamide include:

  • Loss of appetite and weight loss.
  • Nausea.
  • Headache.
  • Agitation, irritability, decreased concentration, or confusion.

The U.S. Food and Drug Administration (FDA) has issued a warning on antiepileptic medicines and the risk of suicide and suicidal thoughts. The FDA does not recommend that people stop using these medicines. Instead, people who take antiepileptic medicine should be watched closely for warning signs of suicide. People who take antiepileptic medicine and who are worried about this side effect should talk to a doctor.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

It may take time and careful, controlled adjustments by you and your doctor to find the combination, schedule, and dosing of medicine to best manage your epilepsy. The goal is to prevent seizures while causing as few side effects as possible. After you and your doctor figure out the medicine program that works best for you, make sure to follow your program exactly as prescribed.

  • Side effects. Zonisamide seems to be well tolerated by most people. A small number of people taking the drug may develop kidney stones, and it may not be safe for people who have reduced kidney function. Zonisamide has been associated with more serious health problems in a few cases, including liver problems, blood problems (such as aplastic anemia), and a life-threatening rash (Stevens-Johnson syndrome). But the risk of these problems is extremely low.
  • Drug interactions. Many medicines for epilepsy can interact with other medicines you may be taking. This means that your epilepsy medicine may not work as well, or it may affect the way another medicine you are taking works. Some of these interactions can be dangerous. Make sure to tell your doctor about all the medicines, herbal pills, and dietary supplements you are taking.
  • Risk of birth defects. All medicines for epilepsy have some risk of birth defects. But the risk of birth defects needs to be carefully compared to other risks to the baby if the mother stops taking her epilepsy medicine. If you are thinking about becoming pregnant, be sure to plan ahead and talk with your doctor about the benefits and risks of taking epilepsy medicine during your pregnancy. It you are already pregnant, it is not too late. The best thing to do is talk to your doctor about your pregnancy before you make any changes to the medicines you are taking.
  • Other concerns. For some people, zonisamide may cause side effects or carry risks that are not yet fully known. Report any unexpected side effects or problems to your doctor.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.



  1. Drugs for epilepsy (2008). Treatment Guidelines From The Medical Letter, 6(70): 37–46.


ByHealthwise Staff
Primary Medical ReviewerSusan C. Kim, MD - Pediatrics
Specialist Medical ReviewerSteven C. Schachter, MD - Neurology
Last RevisedAugust 26, 2011

Last Revised: August 26, 2011

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