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Zonisamide Dosage

Medically reviewed by Last updated on May 11, 2023.

Applies to the following strengths: 100 mg; 25 mg; 50 mg; 100 mg/5 mL

Usual Adult Dose for:

Usual Pediatric Dose for:

Additional dosage information:

Usual Adult Dose for Seizures

16 years of age and older:

  • Initial dose: 100 mg orally once a day
  • Titration: After 2 weeks at 100 mg/day, the dose may be increased to 200 mg/day as either a single or divided dose (100 mg orally 2 times a day) for at least 2 weeks; it can then be increased to 300 mg/day, then 400 mg/day either as a single daily dose or divided into 2 daily doses, with the dose stable for at least 2 weeks to achieve steady state at each level
  • Maintenance dose: 400 mg/day
  • Maximum dose: 600 mg/day

  • This drug may be taken with or without food.
  • Capsules should be swallowed whole.
  • Because of the long half-life of this drug, up to 2 weeks may be required to achieve steady state levels upon reaching a stable dose or following dosage adjustment.
  • The prescriber may wish to prolong the duration of treatment at the lower doses in order to fully assess the effects of this drug at steady state (noting that many of the side effects are more frequent at doses of 300 mg per day and above). Although there is some evidence of greater response at doses above 100 to 200 mg/day, the increase appears small and formal dose response studies have not been conducted.

Use: As adjunctive therapy in the treatment of partial seizures

Usual Pediatric Dose for Seizures

Less than 16 years of age: Not recommended
16 years of age and older: See adult dosing

Renal Dose Adjustments

Because this drug and its metabolites are excreted by the kidneys, patients with renal disease should be treated with caution, and might require slower titration and more frequent monitoring. Therapy should be discontinued in patients who develop acute renal failure or where a clinically significant sustained increase in serum creatinine is observed.

Liver Dose Adjustments

Because this drug is metabolized in the liver, patients with hepatic disease should be treated with caution, and might require slower titration and more frequent monitoring.

Dose Adjustments

When therapy is to be discontinued, it should be withdrawn gradually.


Safety and efficacy have not been established in patients younger than 18 years.

Consult WARNINGS section for additional precautions.


Data not available

Other Comments

Administration advice:

  • This drug may be taken with or without food.
  • Capsules should be swallowed whole and not chewed or crushed.

  • Dermatologic: Development of an unexplained rash.
  • Metabolic: Serum bicarbonate levels, particularly in patients with underlying conditions that might increase the risk of acidosis (e.g., renal disease, severe respiratory disorders, status epilepticus, diarrhea), at increased risk of adverse reactions from metabolic acidosis, or those with symptoms suggestive of metabolic acidosis.
  • Weight loss (particularly substantial undesirable weight loss)
  • Psychiatric: Emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior.
  • Renal: Signs and symptoms of kidney stones (e.g., renal colic, renal pain, or flank pain).

  • Younger patients appear at greater risk for more frequent and severe episodes of therapy-induced metabolic acidosis.
  • Alkali treatment should be considered when therapy is continued in patients with metabolic acidosis.
  • A dietary supplement or increased food intake may be considered if the patient is losing weight or is underweight while on therapy.

Patient advice:
  • Patients, caregivers, and family members should be on the alert for the emergence or worsening of the signs and symptoms of depression, any unusual changes in mood or behavior, or emergence of suicidal thoughts.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.