Zonisamide was first used in Japan in 1972 to treat psychiatric diseases, and it has been widely used to treat epilepsy in Japan and Korea since at least 1990. The Food and Drug Administration (FDA) approved it for use in the United States in March 2000, suggesting that it be used along with other seizure medicines (as adjunctive or add-on therapy) in the treatment of partial seizures in adults.

Zonisamide (zoh-NIH-sah-mide) is the generic name (non-brand name) used in the United States for a widely used seizure medicine. The common brand name for Zonisamide is Zonegran (ZAHN-uh-gran). Zonisamide is marketed in the United States by several manufacturers. The name or appearance may differ in other places.

Please see package insert.


Updated: 16/10/2023

Brand Name(s)

Zonegran, Zonisade

Used to Treat

Temporal Lobe Epilepsy
Focal Impaired Awareness or Complex Partial Seizures
Refractory Seizures
Secondarily Generalized Seizures or Bilateral Tonic Clonic Seizure
Focal Aware Onset Seizure



White capsule with red cap, printed with company logo and "ZONEGRAN 100"

White capsule with gray cap, printed with company logo and "ZONEGRAN 50"

White capsule with white cap, printed with company logo and "ZONEGRAN 25"

Liquid Solution
Zonisade liquid solution prescription bottle

100 mg/5 mL (white to off-white, strawberry flavored), Zonisade

Package Insert

Frequently Asked Questions

    How to take and store Zonisamide?

    Follow your doctor's directions. Call if you have any questions. Usually, your doctor will tell you to start by taking no more than 100 mg each day. After a while the doctor may tell you to take a larger dose to get better control of your seizures. Usually the doctor will tell you to take all the capsules at one time, or perhaps to take capsules twice a day.

    Swallow each capsule whole. Don't bite it or break it open. It's OK to take Zonisamide either with food or without food, but it's important to take it the same way day after day.

    Drink plenty of liquids every day. Doing this may help to prevent kidney stones, a serious problem that affects a small number of people who take Zonisamide.

    Don't take more than the doctor prescribes. Be sure to use only the amount of Zonisamide that your doctor prescribes. Be especially careful if you get a new prescription for a different size of capsule. Don't just continue to take the same number of pills as before.

    If you think you've taken one or two extra capsules, call your doctor for advice. For a larger overdose, call your local poison control center or emergency room right away, unless you have special directions from the doctor.

    Don't stop taking Zonisamide or change the number of capsules you take without talking to your doctor first. Stopping any seizure medicine all at once can cause a serious problem called status epilepticus.

    Store Zonisamide capsules at room temperature, protected from dampness and light. Keep them where children can't get them.

    What if I forget?

    If you forget a dose, take it as soon as you remember. If it is almost time for the next dose, delay that dose for a few hours instead of taking two doses very close together. If you take Zonisamide only once a day, allow an interval of about 12 hours before taking the second dose, and then start a 24-hour schedule again the next day. If you're not sure about what to do, call the doctor's office for advice.

    Do your best to follow the doctor's directions. If you forget doses often, it may be a good idea to get a special pillbox or watch with an alarm to remind you.

    Taking the right amount of seizure medicine on time every single day is the most important step in preventing seizures!

    How does Zonisamide affect the brain?

    Brain cells need to work (fire) at a certain rate to function normally. During a seizure, brain cells are forced to work much more rapidly than normal. Zonisamide helps prevent brain cells from working as fast as a seizure requires them to. In this way, seizures can be stopped when they are just beginning.

    How does the body digest Zonisamide?

    After medicine is swallowed, it must be absorbed into the blood so it can move throughout the body. The process of absorbing, digesting, and excreting a medicine or food is called metabolism. The way the body metabolizes a particular medicine affects how often it must be taken. It also determines whether it will interact with other medicines or be affected by liver disease or kidney disease.

    Zonisamide is broken down (digested) in the liver. People with liver disease must be cautious about taking it. Other people also need to be careful if they take other medicines that are digested in the liver, as many are.

    Because zonisamide is eliminated from the body through the kidneys, the dose may need to be reduced in people with kidney disease.

    How well does the Zonisamide work?

    Doctors have studied large numbers of people with partial seizures to find out how well zonisamide works. Studies have shown that zonisamide works well when added to other seizure medications. Zonisamide is not a perfect add-on seizure medicine for everyone, however. Sometimes people must try a series of combinations before finding what is best for them.

    Some other medicines affect how zonisamide is eliminated from the body, so the dosages may need to be changed with different combinations.

    What are the most common side effects of Zonisamide?

    Many people who take zonisamide don't report any unwanted side effects. Those who experience undesirable effects most often complain of:

    • sleepiness or fatigue
    • dizziness
    • loss of appetite (it's not unusual to lose several pounds)
    • upset stomach
    • headache
    • agitation or irritability
    • weight loss

    Some less-common side effects are:

    • poor coordination or tremor
    • speech problems
    • poor concentration
    • itching
    • vision problems

    If you notice any of these problems, call the doctor's office. Sometimes the doctor can help by changing the amount of zonisamide you take or how you take it. Don't stop taking zonisamide or change the amount you take without the doctor's guidance.

    You should be careful when you first start taking zonisamide. Make sure you don't have a problem with sleepiness or dizziness when driving or doing anything else that might be dangerous.

    Be sure to read about the serious side effects so you will be aware of symptoms that might indicate the beginning of a dangerous reaction to zonisamide. These serious problems are very rare but everyone who takes this medicine should at least be aware of them.

    Allergic reactions
    Approximately 1 in 20 people who take zonisamide have a red rash within the first few weeks of taking it. If this happens, tell the doctor or nurse right away, to be sure that it's not the beginning of a serious problem. It's rare for the rash to be serious, but don't ignore it. It's often necessary to switch to a different seizure medicine

    What are the most serious side effects of Zonisamide?

    Very few people have serious reactions to Zonegran. If you take it, you should be aware of them, however, so you and your family can recognize them. Here's a list of warning signs that may be the start of one of these problems:

    If you notice any of these symptoms, call your doctor right away:

    • Rash
    • Fever, sore throat, sores in your mouth, or easy bruising (could mean a blood problem)
    • Sudden back pain, pain in the stomach area, pain when urinating, or bloody or dark urine (could mean a kidney stone)
    • Decreased sweating or rise in body temperature, especially for a child
    • Depression
    • Thoughts that are unusual for you

    If you notice mood changes with Zonegran, speak to your doctor or nurse. A slight reduction in the dosage may improve your frame of mind. If you had a history of depression before starting Zonegran, your doctor may consider other treatments such as antidepressants or referral to a counselor or psychiatrist.

    The rash may take various forms, from small red spots or blotches on the surface of the skin to large blisters. It may be preceded or accompanied by itchiness. When you first start taking Zonegran (specifically during the first 2 to 4 weeks), watch closely for any signs of a rash. Alert your doctor if you detect changes in your skin. If a rash progresses, you may develop a fever or a feeling of sickness. Occasionally, fever comes before the rash.

    Blood disorders
    A few people have developed blood disorders called aplastic anemia and agranulocytosis while taking zonisamide. The numbers are so small that not much can be said about a possible relationship, but you should tell the doctor if you develop symptoms such as fever, sores in your mouth, or easy bruising.

    Kidney stones
    Kidney stones occurred in about 1 in 80 people, usually after taking Zonegran for 6 to 12 months. Most people who get kidney stones have had kidney stones before. Contact your doctor immediately if you develop symptoms that could indicate a kidney stone, such as sudden back pain, abdominal pain, or blood in the urine. Drinking more fluids may reduce the risk of stone formation. This is especially important if you or someone in your family has had kidney stones, because your risk is greater.

    Decreased sweating
    An effect reported only in children is decreased sweating leading to high body temperature, even heatstroke. This effect is quite rare, but parents of children or teenagers taking Zonegran should be watchful, especially in summer.

    Depression or psychosis
    Tell your doctor if you feel depressed or have thoughts that are unusual for you while you're taking Zonegran. This is unusual but can happen.

    A complete list of all reactions to Zonegran can be found in the package insert, but it is important to remember that only a tiny number of people have any of these serious problems.

    On 2/23/2009, the US Food and Drug Administration issued a warning that the antiepileptic medication zonisamide (Zonegran) can cause metabolic acidosis in some patients. Metabolic acidosis is a condition of excess acidity (low pH) in the blood. The condition can manifest with a variety of symptoms, including chest pains, heart racing, rapid breathing, stomach upset, kidney stones, confusion and other symptoms. People who are already prone to have metabolic acidosis from kidney disease or drugs such as acetazolamide (Diamox), certain diabetes drugs or the ketogenic diet may be more prone to develop zonisamide-induced metabolic acidosis. Young people are also more likely to develop the condition. Metabolic acidosis is detected by measuring blood levels of bicarbonate (worrisome if less than 17 mEq/L), sometimes along with arterial blood gas measurement for levels of oxygen, carbon dioxide and acidity. Once diagnosed, the condition usually is treatable, most directly by stopping zonisamide. The FDA recommended that healthcare professionals measure serum bicarbonate before starting treatment and regularly thereafter.

    On July 10, 2008, an advisory panel was convened by the Food and Drug Administration (FDA) to review data that the FDA had previously collected from drug studies showing an association between many of the antiepileptic drugs (AEDs) and suicidal ideation and behavior, which together are called suicidality. According to the FDA’s Alert, among the patients with epilepsy in these drug studies, 1 out of 1000 people taking the placebo (inactive substance) showed suicidality compared to approximately 3.5 out of 1000 people who took an AED. The FDA advisory panel voted to accept the FDA's data at its meeting on July 10.

    • Taking antiepileptic medicines may increase the risk of having suicidal thoughts or actions;
    • Do not make any changes to the medication regimen without first talking with the responsible healthcare professional;
    • Pay close attention to any day-to-day changes in mood, behavior and actions. These changes can happen very quickly so it is important to be mindful of any sudden differences.
    • Be aware of common warning signs that might be a signal for risk of suicide. Some of these are:
      • Talking or thinking about wanting to hurt yourself or end your life
      • Withdrawing from friends and family
      • Becoming depressed or having your depression get worse
      • Becoming preoccupied with death and dying
      • Giving away prized possessions

    We again urge patients and families to contact their doctor before stopping an epilepsy medication because this may possibly lead to seizures and worsening of mood.

    What else is Zonisamide used for?

    Often doctors find that medicines are useful for more than one purpose. It is legal to prescribe medicines for "off-label uses" even though the FDA has not formally approved such use. Off-label uses of zonisamide include: Lennox-Gastaut syndrome, infantile spasms (West syndrome), progressive myoclonic epilepsy (PME).

    Who should not take Zonisamide?

    The only people who definitely should not take zonisamide are those who are allergic to it or to other medicines in the same family, called sulfonamides. If you have ever been told that you're allergic to sulfa drugs (such as Bactrim or Septra), you should not take zonisamide, or take it only after carefully discussing it with your doctor.

    Because zonisamide is metabolized in the liver and eliminated in the urine, people with liver and kidney disease should be treated with caution. The dosage may have to be increased more slowly.

    Can Zonisamide be taken with other medicines?

    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.

    Your body gets rid of zonisamide quicker if you are also taking certain other seizure medicines, such as:

    • carbamazepine (Tegretol, Tegretol XR, Carbatrol)
    • phenobarbital
    • primidone (Mysoline)
    • phenytoin (Dilantin, Phenytek)

    If this applies to you, your doctor may plan to give you more zonisamide than you would otherwise take.

    What are the effects of Zonisamide on Children?

    Although the Food and Drug Administration (FDA) has not officially approved zonisamide for children, there have been quite a few research studies in which it has been given to children of various ages (even infants) with generally good results. It has been effective in reducing many types of seizures, especially partial seizures, primarily generalized seizures, absence seizures, infantile spasms, and myoclonic seizures.

    Doctors figure out how much medicine to give to young children based mostly on their weight. To keep side effects at a minimum, the doctor probably will prescribe a low dose to start with and increase it slowly. Children usually start with a dose 1 to 2 milligrams (mg) per kilogram (kg) per day. A kilogram equals 2.2 pounds, so a 50-pound child weighs about 23 kilograms and would be started on approximately 25 to 50 mg of zonisamide each day. The doctor would then increase the dosage by a similar amount every 2 weeks, depending on how well the child's seizures are controlled and whether any side effects have appeared. Most children do best at about 8 mg per kg per day (184 mg for a 50-pound child). The highest dose recommended is 12 mg per kg per day.

    The most common side effects in studies of children involved problems with thinking or behavior, followed by stomach upset. One dangerous side effect, decreased sweating with fever, occasionally affects young children but not adults. It is quite unusual but is worth watching out for, especially in summer. Parents whose children are given zonisamide should also watch for the other symptoms of rare but serious reactions that are listed on the serious side effects page.




    If a woman takes Zonisamide during pregnancy will it hurt the baby?

    In the United States, the Food and Drug Administration (FDA) assigns each medication to a Pregnancy Category according to whether it has been proven to be harmful in pregnancy. Zonisamide is listed in Pregnancy Category C. This indicates that caution is advised, but the benefits of the medicine may outweigh the potential risks. Studies in animals have shown some harm to the baby, but there haven't been any good studies of results in women.

    Talk to your doctor or another health professional if you are pregnant or plan to become pregnant. We don't yet have enough information to be able to estimate the risk of various types of birth defects that might occur if zonisamide is taken during pregnancy. We also don't know enough to compare the risk with zonisamide to the risk with other seizure medicines. The risk of birth defects is generally higher for women who take more than one seizure medication and for women with a family history of birth defects.

    Women who are capable of becoming pregnant should take at least 400 mcg (0.4 mg) of folic acid (folate) daily to help prevent a type of birth defect called a neural tube defect. (The best-known of these is spina bifida, in which the spinal cord is not completely enclosed.) Women at high risk, such as those with a history of this kind of defect in a previous pregnancy, should take 4000 mcg (4 mg) daily, beginning before they become pregnant.

    How much zonisamide is passed through breast milk is not known for certain, but the way the body uses it suggests that probably a large portion does enter the milk. If you want to breast-feed your baby, check with your doctor.

    What are the effects of Zonisamide on Seniors

    The effects of zonisamide on seniors are not that well known yet. In general, seniors are more sensitive to the side effects of seizure medicines. Also, because older people are more likely than young ones to have reduced kidney function, their dose of zonisamide will be lower, since zonisamide leaves the body by the kidneys.

    For these reasons, doctors usually start seniors at a low dose and proceed cautiously with any increases.

    What are the dose ranges for Zonisamide?

    The best amount is the amount that completely controls seizures without causing troublesome side effects. It depends on many factors, which are different for every individual. Follow the doctor's directions. Call if you have any questions.

    Zonisamide is usually started at 100 to 200 milligrams per day (mg) for adults. For children, the amount is calculated according to child's weight. Children usually start at 2 to 4 mg per kilogram (kg, about 2.2 pounds) per day, divided into two doses.

    Dosages should be increased at 2-week intervals to an ongoing dose of 400 to 600 mg per day for adults and 4 to 8 mg per kg per day for children. Some people may need (and be able to tolerate) higher dosages.

    Read the package insert of Zonisamide

    In the United States, companies that manufacture medicines are required to publish certain kinds of information about each product. This document is commonly known as a “package insert” because it is usually included with each package of the medicine.

    You can also read these documents (also called "prescribing information") online. The U.S. package insert for Zonegran (zonisamide) is found at:

    Some of the information may differ in other countries.

    To learn how to read and understand a package insert, see  "How to read a package insert."


    Primary Generalized Epilepsy

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