Zonisamide

Introduction

Written by Lee Holland, PharmD
Medically reviewed by Rosanna Sutherby, PharmD
Updated on July 27, 2023

Zonisamide (zoe NIS a mide) is a generic medication prescribed for certain people with focal onset seizures (also known as partial seizures). It’s prescribed with other medications for this condition. Zonisamide belongs to a group of drugs called sulfonamide epilepsy medications. (Sulfonamides are also known as sulfa drugs.)

Common questions about zonisamide

Below you’ll find answers to a few commonly asked questions about zonisamide.

Can zonisamide be used for weight loss?

Zonisamide isn’t approved as a weight loss aid.

That said, doctors sometimes prescribe it to treat binge eating disorder, but this is an off-label use. (With off-label use, doctors prescribe a drug for a purpose other than what it’s approved for.) Zonisamide may help people with this condition lose weight.

If you’d like to know more about this, talk with your doctor.

What brand names are available for zonisamide?

Zonisamide oral capsule is a generic medication. The brand-name version of zonisamide oral capsule is called Zonegran. There’s also a liquid form of zonisamide available as the brand-name drug Zonisade. But the liquid form isn’t available in a generic version.

A generic medication is an identical copy of the active drug in a brand-name medication. (An active drug is the ingredient that makes a medication work.) Generic drugs are believed to be as effective and safe as brand-name drugs. And generic drugs typically cost less compared to brand-name drugs.

If you’d like to know more about generic and brand-name zonisamide, talk with your doctor or pharmacist.

How does zonisamide work? And how long does it take to start working?

Zonisamide is prescribed for adults and some children with focal onset seizures, which are also called partial seizures. During a seizure, a person has uncontrolled electrical surges in their brain.

Zonisamide works by stopping these surges in brain cells. It’s not known for sure how zonisamide works. But it may work by regulating how brain cells use calcium and sodium.

Zonisamide can take up to 2 weeks before it starts working. After 2 weeks of treatment at a low dose, your doctor may increase your dose if needed.

If you’d like to know more about this, talk with your doctor or pharmacist.

Uses of zonisamide

The Food and Drug Administration (FDA) approves prescription drugs such as zonisamide for certain conditions. Approved uses for zonisamide are described below.

Use for seizures

Doctors may prescribe zonisamide oral capsule to help prevent focal onset seizures, which are also called partial seizures. It’s used for this purpose in people ages 16 years and older with epilepsy. It’s usually prescribed as a long-term treatment.

With partial seizures, you have uncontrolled electrical surges in some brain cells. These seizures may cause muscle twitches or weakness, unusual movements, loss of consciousness, and other symptoms.

Zonisamide is prescribed together with other drugs for partial seizures.

Doctors may not prescribe zonisamide oral capsule in certain situations, such as to people who have an allergy to sulfa drugs.

Interactions and warnings for zonisamide

Below you’ll find information about zonisamide’s possible interactions and warnings.

Interactions of zonisamide

Certain things may affect how a drug works. These include getting vaccines, consuming alcohol or certain foods, or taking the drug with other medications. This effect is called a drug interaction.

Before you take zonisamide, ask your doctor to check for possible interactions. Be sure to tell them about any of the following you take or use:

• prescription or over-the-counter drugs
• vitamins, herbs, or supplements

To learn about drug-condition interactions, see the “Warnings for zonisamide” section below.

Warnings for zonisamide

Zonisamide should not be taken by certain people. This includes people who have an allergy to sulfa drugs.

Also, zonisamide could cause harm to people with certain health conditions. This effect is called a drug-condition interaction. Other factors can also affect whether zonisamide is a safe option for you. These warnings may differ based on the form of zonisamide you take.

Ask your doctor about specific warnings for zonisamide, and be sure to tell your doctor about your:

• current health, including any allergies to medications
• past health conditions or surgeries

Allergic reaction

Zonisamide can cause an allergic reaction in some people. This includes people who have an allergy to sulfa drugs. Severe allergic reactions are rare but possible.

If you’ve had an allergic reaction to zonisamide or any other sulfa drug, your doctor will likely not prescribe zonisamide. They can tell you about medications that are safer options for you.

A mild allergic reaction may cause the following symptoms:

• skin rash
• itchiness
• flushing (temporary warmth, redness, or deepening of skin color)

A severe allergic reaction may cause the following symptoms:

• swelling under your skin, usually in your hands, feet, eyelids, or lips
• swelling of your mouth, throat, or tongue, which can cause breathing problems

If you have an allergic reaction to zonisamide, call your doctor right away. If you have severe symptoms, call 911 or a local emergency number.

Overdose of zonisamide

You should not take more zonisamide than your doctor prescribes. For some drugs, doing so may lead to harmful effects or overdose.

If you think you’ve taken too much zonisamide, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have concerning symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.

Pregnancy or breastfeeding and zonisamide

Information about zonisamide and pregnancy and breastfeeding is described below.

Zonisamide and pregnancy

There are risks to taking zonisamide during pregnancy. But there are also risks with having partial seizures while pregnant. (Keep in mind that zonisamide is used for managing focal onset seizures, which are also called partial seizures.)

If you’re planning a pregnancy or can become pregnant, talk with your doctor about partial seizure treatment options during pregnancy. Together, you can discuss the risks and benefits of your treatment options and decide whether you should take zonisamide during pregnancy.

Zonisamide and breastfeeding

There are risks to taking zonisamide while breastfeeding. But there are also risks with having partial seizures during this time. (Keep in mind that zonisamide is used for managing focal onset seizures, which are also called partial seizures.)

If you’re planning to breastfeed, talk with your doctor about partial seizures treatment options. Together, you can discuss the risks and benefits of your treatment options and decide whether you should take zonisamide during this time. Your doctor may recommend other healthy ways to feed your child.

Side effects of zonisamide

Zonisamide may cause mild or serious side effects. More common mild side effects of zonisamide and its serious side effects are listed below. This article doesn’t include all possible side effects of the drug. Side effects can vary based on your age, overall health, and any other medications you take.

To learn more about zonisamide’s side effects, ask your doctor or pharmacist. You can also refer to the prescribing information for zonisamide listed in the “Resources” section.

Mild side effects

More common mild side effects reported with some forms of zonisamide are listed below. These side effects may differ based on the form of zonisamide you take.

This article doesn’t include all possible mild side effects of the drug. To learn more about zonisamide’s side effects based on the form, refer to the prescribing information for zonisamide listed in the “Resources” section.

With many drugs, mild side effects may go away within a few days or a couple of weeks. If the side effects are bothersome, tell your doctor or pharmacist. They may be able to suggest ways to manage them.

Zonisamide oral capsule’s mild side effects include:

• sleepiness
• loss of appetite
• dizziness
• mild memory problems or trouble concentrating
• mild allergic reaction*

* For details about this side effect, see the “Interactions and warnings for zonisamide” section.

Serious side effects

Serious side effects of zonisamide are listed below.

This article doesn’t include all possible serious side effects of the drug. To learn more about zonisamide’s side effects, refer to the prescribing information for zonisamide listed in the “Resources” section.

With many drugs, serious side effects are possible but not common. If you have serious side effects from this drug, call your doctor right away. If you’re having severe symptoms or a medical emergency, call 911 or a local emergency number.

In general, zonisamide’s serious side effects include:

• serious skin reactions called Stevens-Johnson syndrome and toxic epidermal necrolysis, which may be life threatening
• dangerously high fever and reduced sweating in children*
• vision problems that may cause blindness if untreated
• kidney stones
• suicidal thoughts or actions
• problems thinking, remembering, paying attention, or speaking
• increased level of acid in the blood
• changes in blood cell levels
• severe allergic reaction†

* Zonisamide is not approved for use in children younger than 16 years of age.
† For details about this side effect, see the “Interactions and warnings for zonisamide” section.

Suicide prevention

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

• Call the 988 Suicide and Crisis Lifeline at 988.
• Text HOME to the Crisis Textline at 741741.
• Not in the United States? Find a helpline in your country with Befrienders Worldwide.
• Call 911 or your local emergency services number if you feel safe to do so.

If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.

If you are not in the same household, stay on the phone with them until help arrives.

What to ask your doctor

Let your doctor know if you have questions about zonisamide or would like more details about it.

Here’s a list of some possible questions you may want to ask your doctor:

• Will I take zonisamide with other medications for my condition?
• Should I use birth control while taking zonisamide?
• How is zonisamide different from other drugs used to treat my condition?
• What medications should I avoid taking while I’m taking zonisamide?

Resources

• Food and Drug Administration. (2023). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/index.cfm
• Ricca V, et al. (2009).Zonisamide combined with cognitive behavioral therapy in binge eating disorder. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2801482/
• Zonisamide – zonisamide capsule. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/ab0631ca-5339-4570-bc27-f1dd92de1d6f/spl-doc

Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.