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Apr 24, 2024


Epilepsy Management with Zonisamide

What is Zonisamide?

Zonisamide is a prescription medication that belongs to a class of drugs known as anticonvulsants. These medications work by interacting with brain chemicals called neurotransmitters. By regulating abnormal electrical activity in the brain, Zonisamide helps stabilize neural functions and prevent seizures.


Approved by the Food and Drug Administration (FDA) in March 2000, Zonisamide is primarily prescribed to manage epilepsy, a neurological disorder marked by recurring seizures. These are sudden, brief disruptions in the brain's electrical activity that can affect various mental and physical functions.

Zonisamide is approved to aid in controlling partial seizures, which occur in just one part of the brain. Symptoms of partial seizures can include jerking limb movements, altered consciousness, or sensory disturbances. It is typically used in combination with other medications as an adjunctive therapy for adults and adolescents aged 16 and older.

Off-Label Use

While the FDA has approved Zonisamide for managing partial seizures, it is not uncommon for doctors to prescribe it for other conditions. This practice, known as "off-label" use, remains legal and is widely practiced despite the lack of formal FDA approval for these additional uses. Conditions for which Zonisamide is commonly prescribed off-label include:

  • Lennox-Gastaut syndrome
  • Infantile spasms (West syndrome)
  • Progressive myoclonic epilepsy (PME)

Zonisamide stands as a crucial tool in the ongoing effort to provide better quality of life for those affected by epilepsy and other related conditions.

Dosage and Instructions

Zonisamide is available as a capsule in the following strengths:

  • 25 mg
  • 50 mg
  • 100 mg

You can take Zonisamide with or without food, and it is typically administered either once or twice daily depending on your needs. If you experience dizziness or drowsiness, your doctor might suggest taking the medication just once a day, preferably in the evening. It's important to have a conversation with your healthcare provider to determine if this dosing schedule is right for you.

Adjusting to the right dose of Zonisamide can take some time. Initially, your doctor will likely prescribe a lower dose and monitor your response to the medication. Depending on how you tolerate Zonisamide and any side effects you experience, your doctor may gradually increase your dose.

It usually takes about two weeks for a new dose to stabilize in your body. After this period, your healthcare provider can evaluate whether further adjustments are necessary to find the most effective dose for you.

Missed dose

If you miss a dose of Zonisamide, take it as soon as you remember. However, if it's almost time for your next scheduled dose, skip the missed dose and continue with your regular dosing schedule. Do not take two doses at once as this can lead to complications.

It's important to maintain a consistent medication schedule to avoid the risks associated with abruptly stopping Zonisamide. Suddenly discontinuing the medication can trigger the return or worsening of seizures. Always consult with your doctor before making any changes to how you take your medication. If you need to stop taking Zonisamide after long-term use, your doctor will guide you in gradually decreasing your dose to safely discontinue use.

Side Effects

Common Side Effects
  • Dizziness
  • Headache
  • Decreased appetite
  • Weight loss
  • Abdominal pain
  • Diarrhea, constipation, and/or indigestion
  • Agitation or irritability
  • Problems with concentration or memory
  • Dry mouth
  • Changes in taste
  • Experiencing tingling in your arms, hands, and/or feet
  • Having double vision
  • Sleepiness or fatigue.

It is important to be cautious when driving or engaging in activities that require alertness until you understand the effects of this medication on your body.

If you are experiencing any of these side effects, talk with your doctor to determine whether a dose adjustment or switching to a different medication would be beneficial for you.

Serious Side Effects

When taking Zonisamide, it's important to be aware of potential serious side effects. If you experience any of the following, contact your doctor immediately:

  • Infection Signs: Fever, sore throat, mouth sores, or easy bruising could indicate an infection
  • Severe Skin Reactions: Symptoms like skin blistering and peeling, fever, flu-like symptoms, or difficulty swallowing may occur
  • Kidney Problems: Watch for sudden back pain, stomach pain, pain during urination, or the presence of bloody or dark urine, which could signify kidney stones
  • Heat Stroke: Symptoms include sweating less than usual, elevated body temperature, or fever
  • Suicidal Behavior: Be alert for worsening depression, mood or behavior changes, or suicidal thoughts.
  • Metabolic Acidosis: This rare condition increases blood acid levels, possibly leading to kidney stones, weakened bones (increasing fracture risk), and can affect brain function. Symptoms include fatigue, difficulty concentrating, or vomiting.
  • Serious Allergic Reactions: Signs to watch for include rashes, hives, difficulty breathing, or swelling of the face, lips, tongue, or throat

It is crucial to stop taking the medication and seek immediate medical attention if you experience any of these serious side effects.


Sulfa Allergy Caution
Zonisamide is part of the sulfonamide (sulfa) drug family. If you are allergic to sulfa medications like Bactrim (sulfamethoxazole/trimethoprim), you should avoid taking Zonisamide due to the risk of severe allergic reactions. Symptoms such as skin rashes, facial or throat swelling, or difficulty breathing require immediate medical attention or a visit to the emergency room.

Alcohol and Sedatives
While on Zonisamide, avoid alcohol and medications that cause drowsiness. These can intensify side effects like sleepiness, dizziness, and reduced alertness, which could dangerously affect your breathing.

Liver Disease Considerations
Individuals with liver disease need to be cautious, as Zonisamide is metabolized in the liver. The same caution applies to those on other medications processed by the liver, which includes many common drugs.

Kidney Disease and Dosing
Since Zonisamide is excreted through the kidneys, those with kidney disease may need dose adjustments to safely use this medication.


Zonisamide may interact with certain medications or supplements. Always inform your doctor and pharmacist about any other medications or supplements, including prescribed and over-the- counter, vitamins, and dietary or herbal supplements, that you are currently taking.

It is recommended to avoid using Zonisamide with medications that could increase your risk of certain side effects, including the following:

  • Lipase inhibitors, such as Orlistat
  • Sulfa medications, such as Bactrim (sulfamethoxazole/trimethoprim), or Sulfasalazine (Azulfidine)
  • Antibiotics, such as Methenamine
  • Vitamin D3, Calcifediol

Pregnant or breastfeeding


Zonisamide is classified under Pregnancy Category C, which suggests that while there may be potential risks, the benefits could outweigh these risks in some cases. Animal studies have shown adverse effects on the fetus, but human studies are not conclusive enough to clearly define the risks. If you are pregnant or planning to become pregnant, discuss the use of Zonisamide with your doctor, as the data is currently insufficient to fully assess the risk of birth defects associated with its use during pregnancy.


ZThe extent to which Zonisamide is transferred to breast milk is not fully known. However, based on how the body metabolizes the drug, it is likely that a significant amount may pass into the milk. If you are considering breastfeeding, consult your doctor to discuss the potential implications and to receive appropriate guidance.

Speak With Your Doctor

You should consult your doctor about the possibility of using Zonisamide, especially if you have epilepsy and other medications have not effectively controlled your seizures. Zonisamide has been proven to help reduce both the frequency and severity of seizures, which could significantly enhance your quality of life.

While it offers these benefits, it's also important to weigh the potential risks. Common side effects include dizziness, fatigue, and decreased appetite. More serious but less common risks involve developing conditions like metabolic acidosis or kidney stones.

Given these considerations, Zonisamide might be an excellent treatment option for some individuals. Discussing with your doctor will help determine if it's suitable for your specific situation.

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