Do not take Zonisade if you:

• are allergic to sulfonamides or zonisamide.

What is the most important information I should know about ZONISADE?

ZONISADE may cause serious skin reactions that can cause death. These serious skin reactions may include a severe rash with blisters and peeling skin, especially around the mouth, nose, eyes and genitals (Stevens-Johnson syndrome). ZONISADE may also cause a rash with blisters and peeling skin over much of the body (toxic epidermal necrolysis). Call your healthcare provider right away if you develop a skin rash.

ZONISADE can cause blood cell changes such as reduced red and white blood cell counts. Call your healthcare provider right away if you develop fever, sore throat, sores in your mouth, or easy bruising.

ZONISADE can cause other types of allergic reactions or serious problems that may affect different parts of the body such as your liver, kidneys, heart, or blood cells. You may or may not have a rash with these types of reactions. These reactions can be very serious and can cause death. Call your healthcare provider right away if you have:

ZONISADE may cause decreased sweating and increased body temperature (fever). People, especially children, should be watched for signs of decreased sweating and fever, especially in hot temperatures. Some people may need to be hospitalized for this condition. If you have decreased sweating with or without a fever, call your healthcare provider right away.

ZONISADE may cause eye problems. Serious eye problems include:

• any sudden decrease in vision with or without eye pain and redness
• a blockage of fluid in the eye causing increased pressure in the eye (secondary angle closure glaucoma)

These eye problems can lead to permanent loss of vision if not treated.

Call your healthcare provider right away if you have any new eye symptoms, including any new problems with your vision.

Like other antiepileptic drugs, ZONISADE may cause suicidal thoughts. Call a healthcare provider right away if you have any of these symptoms, especially if they are new, worse, or worry you:

Suicidal thoughts or actions can be caused by things other than medicines. If you have suicidal thoughts or actions, your healthcare provider may check for other causes.

ZONISADE can cause abnormal heart rhythms, which may be life-threatening. This risk may be increased in patients with underlying heart problems. Call your healthcare provider right away if you have:

ZONISADE can increase the level of acid in your blood (metabolic acidosis). If left untreated, metabolic acidosis can cause brittle or soft bones (osteoporosis, osteomalacia, osteopenia), kidney stones and can slow the rate of growth in children. Metabolic acidosis can happen with or without symptoms. Call your healthcare provider right away if you have any of these symptoms:

Your healthcare provider should do a blood test to measure the level of acid in your blood before and during your treatment with ZONISADE.

ZONISADE may cause problems with thinking and alertness. ZONISADE may affect how you think and cause confusion, problems with concentration, attention, memory, or speech. ZONISADE may cause depression or psychotic symptoms (such as seeing or hearing things that are really not there), tiredness, and sleepiness.

Do not stop Zonisade without first talking to a healthcare provider:

• Stopping ZONISADE suddenly can cause serious problems.
• Stopping a seizure medicine suddenly in a patient who has epilepsy can cause seizures that will not stop (status epilepticus).

What are the possible side effects of ZONISADE?

ZONISADE can cause serious side effects, including:

• high blood ammonia levels. High ammonia in the blood can affect your mental status, slow your alertness, make you feel tired, or cause vomiting. Call your healthcare provider right away if you develop unexplained tiredness, vomiting, slow alertness or changes in your mental status.
• kidney stones. Drink plenty of fluids while you take ZONISADE to decrease your chances of getting kidney stones. Call your healthcare provider right away if you get back pain, stomach pain, or blood in your urine.
• decrease in kidney function. ZONISADE may cause a decrease in kidney function. Your healthcare provider should do a blood test to measure your kidney function before and during treatment with ZONISADE.

Before taking ZONISADE, tell your healthcare provider about all of your medical conditions, including if you:

• have or have had depression, mood problems or suicidal thoughts or behavior.
• have heart problems
• have kidney problems.
• have liver problems.
• have a history of metabolic acidosis (too much acid in your blood).
• have weak, brittle bones or soft bones (osteomalacia, rickets, osteopenia, or osteoporosis).
• have a growth problem.
• are on a diet high in fat called a ketogenic diet.
• have diarrhea.
• have high blood levels of ammonia.
• are pregnant or plan to become pregnant. ZONISADE may harm your unborn baby. Women who can become pregnant should use effective birth control. Tell your healthcare provider right away if you become pregnant or think you may be pregnant while taking ZONISADE. You and your healthcare provider should decide if you should take ZONISADE while you are pregnant.
• are breastfeeding or plan to breastfeed. ZONISADE can pass into your breast milk. It is not known if ZONISADE in your breast milk can harm your baby. Talk to your healthcare provider about the best way to feed your baby if you take ZONISADE. If you breastfeed while taking ZONISADE, check your baby and call your healthcare provider right away if your baby has increased sleepiness, decreased hunger, or elevated body temperature.

Tell your healthcare provider about all the medicines you take, including

• Prescription and over-the-counter medicines, vitamins, and herbal supplements.

The most common side effects of ZONISADE include:

Tell your healthcare provider about any side effect that bothers you or that does not go away. These are not all the possible side effects of ZONISADE. Call your doctor for medical advice about side effects.