Reviewed on 9/2/2021

What Is Zonisamide and How Does It Work?

Zonisamide is a sulfonamide anticonvulsant and a carbonic anhydrase inhibitor indicated as adjunctive therapy in the treatment of partial seizures in adults with epilepsy.

  • Zonisamide is available under the following different brand names: Zonegran.

What Are Dosages of Zonisamide?

Dosages of Zonisamide:

Dosage Forms and Strengths


  • 25 mg
  • 50 mg
  • 100 mg

Dosage Considerations – Should be Given as Follows:

Partial Seizures

  • Adult: Initial: 100 mg orally once/day
  • Titrate up by 100 mg increments every 2 weeks to no more than 600 mg orally once/day (may divide every 12 hours after 1st week)
  • Adolescents over 16 years: Same as in adults

Weight Loss (Off-label)

  • 100 mg increments every 2 weeks to no more than 600 mg orally once/day (may divide every 12 hours after the first week); use 600 mg/day in patients who have not lost at least 5% of their initial body weight

Dosing Modifications

  • Renal impairment: Slower titration and more frequent monitoring advised; not recommended if patient's glomerular filtration rate is less than 50 mL/min
  • Hepatic impairment: Slower titration and more frequent monitoring advised
  • Geriatric: Administer as in adults; initiate dosing at the lower end of the dosing range
  • Children under 16 years: Not recommended


What Is Epilepsy? Symptoms, Causes, and Treatments See Slideshow

What Are Side Effects Associated with Using Zonisamide?

Common side effects of Zonisamide include:

  • Headache
  • Nausea
  • Agitation
  • Abdominal pain
  • Loss of control of bodily movements
  • Confusion
  • Depression
  • Double vision
  • Trouble sleeping (insomnia)
  • Diarrhea
  • Speech disorder
  • Flu-like symptoms
  • Kidney stones
  • Irregular, repetitive eye movements
  • Numbness and tingling
  • Changes in taste
  • Weight loss
  • Anxiety
  • Rash
  • Constipation
  • Runny or stuffy nose
  • Dry mouth
  • Tired feeling
  • Loss of balance or coordination
  • Sore throat
  • Cough
  • Blurred vision

Serious side effects of zonisamide include:

  • Increased or worsening seizures
  • Lightheadedness
  • Shortness of breath
  • Rapid heart rate
  • Trouble concentrating
  • Fever
  • Chills
  • Sores in your mouth and throat
  • Severe pain in your lower back
  • Blood in your urine
  • Feeling very thirsty or hot
  • Being unable to urinate
  • Severe skin reaction

Postmarketing side effects of zonisamide reported include:

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Zonisamide?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Zonisamide has no known severe interactions with other drugs.
  • Serious interactions of zonisamide include:
  • Zonisamide has moderate interactions with at least 150 different drugs.
  • Zonisamide has mild interactions with at least 76 different drugs.

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more information about this medicine.

What Are Warnings and Precautions for Zonisamide?


This medication contains zonisamide. Do not take Zonegran if you are allergic to zonisamide or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.


Effects of Drug Abuse

  • No information available

Short-Term Effects

  • Sedation may occur.
  • Slowing and fatigue may occur within the first month of treatment.
  • See "What Are Side Effects Associated with Using Zonisamide?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Zonisamide?"


  • Maintain fluid intake due to risk of kidney stone formation
  • Discontinue treatment if a significant sustained increase in creatinine occurs
  • Risk of serious skin reactions; consider discontinuation in patients who develop an unexplained rash
  • Sedation may occur
  • Slowing and fatigue may occur within the first month of treatment
  • Risk of rare, but potentially fatal, anaphylactic reactions (including blood dyscrasias and skin reactions)
  • Risk of metabolic acidosis
  • Use appropriate precautions for handling and disposal
  • An increase in suicidal ideation may occur with use; see FDA Warning on potential suicidal behavior
  • Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS), also known as multi-organ hypersensitivity reported; early manifestations of hypersensitivity (e.g., fever, lymphadenopathy) may be present even though rash not evident; if such signs or symptoms present, evaluate immediately; discontinue therapy if an alternative etiology for signs or symptoms cannot be established

Pregnancy and Lactation

  • There are no available data on the use of zonisamide in pregnant women and the risk of major birth defects or miscarriage. However, in pregnant rats and rabbits administered 50 and 6.8 times the human dose, respectively, decreases in body weight, decreased fetal resorption, and delayed fetal ossification were observed
  • There are no data regarding the presence of zonisamide in human milk or effects on the breastfed child
  • Diuretics can suppress lactation
  • Consult your doctor before breastfeeding


See Images
Medscape. Zonisamide.
RxList. Zonegran.

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