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Overview: Zonisamide is used to treat certain types of seizures. Common side effects include drowsiness and dizziness. Do not drive or do other activities that require alertness or coordination until you know how zonisamide affects you. Call your health care provider right away if you get a rash, unusual bleeding, sore throat, fever, eye pain, vision changes, confusion, vomiting, or changes in your mood or behavior. Do not stop this medicine without talking with your health care provider.

Uses

What is zonisamide used for?

Zonisamide is commonly used to treat certain types of seizures.

Zonisamide may also be used for other conditions as determined by your health care provider.

How does zonisamide work (mechanism of action)?

Seizures happen when too many nerve signals are sent between brain cells too quickly. Zonisamide is thought to work by slowing down overactive brain signals and making seizures less likely.

How is zonisamide supplied (dosage forms)?

Brands and other names

  • Zonegran
  • Zonisade

Dosage forms and strengths

  • 25 mg oral capsules
  • 50 mg oral capsules
  • 100 mg oral capsules
  • 100 mg/5 mL oral suspension

How should I store zonisamide?

Zonisamide should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place. Protect from light. Throw the liquid medicine away 30 days after first opening the bottle. 

Side Effects

What are the most common side effects of zonisamide?

The most common side effects of zonisamide are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Drowsiness
  • Loss of appetite 
  • Dizziness
  • Trouble with balance or coordination
  • Feeling agitated or irritable
  • Problems with memory or concentration

There may be other side effects of zonisamide that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of zonisamide?

While less common, the most serious side effects of zonisamide are described below, along with what to do if they happen.

Severe Skin Reactions. Zonisamide can cause severe skin reactions, called Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), that can lead to death if not treated. If you develop a rash, call your health care provider right away. Get emergency help if you have any of the following symptoms of SJS or TEN.

  • Painful red or purple skin that looks burned and peels off
  • Flat red rash or blisters on your skin, mouth, nose, and genitals
  • Red, painful, watery eyes

Blood Disorders. Zonisamide can cause blood disorders, such as agranulocytosis and aplastic anemia. Get help right away if you have any of the following symptoms of blood disorders.

  • Fever
  • Shortness of breath
  • Pale or yellowish skin
  • Easy bruising or bleeding
  • Frequent infections
  • Unusual weakness or tiredness
  • Dizziness, lightheadedness, or feeling like you are about to pass out
  • Headache
  • Fast or abnormal heartbeat

Severe Allergic Reactions. Zonisamide may cause allergic reactions, including a specific type of allergic reaction called DRESS. DRESS stands for drug reaction with eosinophilia and systemic symptoms. It is also sometimes called multiorgan hypersensitivity. This is a reaction that can affect multiple parts of the body, including your liver, kidneys, and heart. Get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Shortness of breath, trouble swallowing, or throat tightness
  • Swelling in your feet, ankles, or legs
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain
  • Dark-colored pee
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Decreased Sweating and Increased Body Temperature. Zonisamide can reduce your body’s ability to sweat. This can lead to high body temperatures (or fever) and possibly a heatstroke, especially in children. This risk may be higher if you are taking certain other medicines. Follow any instructions from your health care provider about monitoring your temperature, especially during the summer. Tell your health care provider right away if you notice you are not sweating normally or if you develop a fever.

Eye Problems. Zonisamide may make it harder to see faraway objects (short sight). It may also increase pressure inside the eye and cause or worsen narrow-angle glaucoma, which can lead to blindness. Tell your health care provider right away if you have any of the following symptoms.

  • Trouble seeing faraway objects
  • Loss of vision
  • Eye pain or redness
  • Severe headache or vomiting
  • Seeing bright, colorful circles around lights (vision halos)

Suicidal Thoughts and Actions. Zonisamide may cause suicidal thoughts or actions in a small number of people. If you are about to harm yourself, call 911 or call or text 988, the Suicide & Crisis Lifeline. Call your health care provider right away if you have any of the following symptoms.

  • New or increased thoughts of suicide or death
  • Suicide attempt
  • New or increased feelings of anxiety, depression, or other unusual changes in mood or behavior

Metabolic Acidosis. Zonisamide can cause a condition called metabolic acidosis. This happens when there is too much acid in the blood. If this condition is not treated, it can cause kidney stones, slow growth in children, or harm to the fetus if you are pregnant. Your bones can also become soft or brittle (osteoporosis, osteomalacia or rickets, osteopenia). Keep all appointments to have your blood checked. Tell your health care provider right away if you have any of the following symptoms of metabolic acidosis.

  • Fast breathing or heartbeat
  • Headache
  • Feeling confused, weak, or tired
  • Not feeling hungry
  • Nausea or vomiting

Hallucinations or Psychotic-Like Behaviors. Zonisamide may cause hallucinations or psychotic-like behaviors. Tell your health care provider right away if you have any of the following symptoms or if you have been told by others you have these symptoms.

  • Hearing, seeing, smelling, tasting, or otherwise perceiving things that others do not
  • Delusional thoughts, such as false beliefs that you are being controlled
  • Disorganized thoughts, such as jumping between topics or having a hard time focusing
  • Sudden decline in self-care, such as personal hygiene or academic/work performance
  • Aggressive behavior

Nervous System Problems. Zonisamide can make you dizzy or sleepy. It can also cause trouble talking, remembering, or concentrating and may affect your alertness or coordination. Do not drive or do other activities that require alertness or coordination until you know how zonisamide affects you.

High Ammonia Levels and Encephalopathy. Zonisamide can increase ammonia levels in your blood and cause encephalopathy. You may need a blood test to check the amount of ammonia in your blood. Tell your health care provider right away if you develop any of the following symptoms of high ammonia levels or encephalopathy.

  • Nausea and vomiting
  • Unexplained tiredness
  • Confusion or slowed thinking
  • Slowed reaction time
  • Trouble with balance or coordination

Kidney Stones. Zonisamide may cause kidney stones. Drinking plenty of water can help prevent kidney stones. Tell your health care provider right away if you develop severe pain in your side or back or have blood in your urine (pee). Your pee may look pink, red, or brown.

Kidney Damage. Kidney damage can happen when taking zonisamide. Call your health care provider right away if you have any of the following symptoms of kidney damage.

  • Reduced need to pee
  • Swelling in your feet, ankles, or legs
  • Weakness or unusual tiredness
  • Difficulty catching your breath or chest pain/pressure
  • Confusion
  • Nausea
  • Seizures

Warnings & Precautions

Who should not use zonisamide?

Allergies to Ingredients. People who are allergic to any of the following should not take zonisamide.

  • Zonegran
  • Zonisade
  • Zonisamide
  • Any medicine known as a sulfonamide
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific zonisamide products they stock.

What should I know about zonisamide before using it?

Do not take zonisamide unless it has been prescribed to you by a health care provider. Take it as prescribed.

If you are taking the zonisamide liquid, u​se an accurate measuring device to measure your dose. A household spoon is not an accurate measuring device and may cause you to take the wrong dose. Ask your pharmacist to recommend a right measuring device. Shake well before each use. 

Do not share zonisamide with other people, even if they have the same condition as you. It may harm them.

Keep zonisamide out of the reach of children.

While zonisamide helps make seizures less likely, it does not cure them. Do not stop taking zonisamide without talking to your health care provider. Stopping zonisamide suddenly may cause an increase in seizure activity, which can be serious.

What should I tell my health care provider before using zonisamide?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if zonisamide is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Liver or kidney problems
  • Mental health problems, such as depression, thoughts of suicide, or other mood problems
  • History of metabolic acidosis
  • Weak, soft, or fragile bones
  • Are following a ketogenic diet
  • High blood ammonia levels
  • Diarrhea

Other Medicines and Supplements. Zonisamide may interact with other medicines and supplements. Before taking zonisamide, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. Zonisamide may cause harm to a fetus. Tell your health care provider right away if you are pregnant or plan to become pregnant. Your health care provider will let you know if you should take zonisamide while you are pregnant or trying to get pregnant. If you become pregnant while taking zonisamide, you can sign up for the North American Antiepileptic Drug Pregnancy Registry by calling 888-233-2334 or at www.aedpregnancyregistry.org. This registry collects safety information about the use of seizure medicines during pregnancy.

Breastfeeding. Zonisamide passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should take zonisamide while breastfeeding.

Interactions

Does zonisamide interact with foods or drinks?

There are no known interactions between zonisamide and foods or drinks.

It is unknown if drinking alcohol will affect zonisamide. The risk of dizziness and drowsiness may increase if you drink alcohol while taking zonisamide. It is best to avoid drinking alcohol while you are taking this medicine.

Does zonisamide interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking zonisamide.

  • Any other medicine that causes dizziness and sleepiness, such as prescription pain medicines, sleep medicines, or medicines for anxiety
  • Topiramate (Qudexy XR, Topamax, Trokendi XR), which is a medicine commonly used to treat seizures or prevent migraine
  • Divalproex sodium, valproate sodium (Depakote and others), or valproic acid, which are medicines used for seizures and other conditions
  • A carbonic anhydrase inhibitor, such as acetazolamide (Diamox) or methazolamide
  • Rifampin (Rifadin), which is a medicine commonly used to treat an infection called tuberculosis

Some other medicines may alter the blood levels of zonisamide. Tell your health care provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with zonisamide. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much zonisamide?

If you or someone else has used too much zonisamide, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of zonisamide?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.