From the FDA Drug Label
Zonisamide capsules USP are given orally and can be taken with or without food. The initial dose of zonisamide should be 100 mg daily. After two weeks, the dose may be increased to 200 mg/day for at least two weeks It can be increased to 300 mg/day and 400 mg/day, with the dose stable for at least two weeks to achieve steady state at each level. Evidence from controlled trials suggests that zonisamide doses of 100 to 600 mg/day are effective, but there is no suggestion of increasing response above 400 mg/day
The recommended dosage of zonisamide (Zonegran) is:
- Initial dose: 100 mg daily
- Titration: increase dose to 200 mg/day after 2 weeks, and further to 300 mg/day and 400 mg/day with at least 2 weeks at each level
- Effective dose range: 100 to 600 mg/day, with no increase in response suggested above 400 mg/day 1
From the Research
Zonisamide is typically started at a low dose of 100 mg once daily and gradually increased to minimize side effects, with a recommended maintenance dose ranging from 200-400 mg daily for adults with epilepsy, as supported by the most recent and highest quality study 2.
Key Considerations
- The medication should be taken consistently with or without food, and abrupt discontinuation should be avoided to prevent seizure risk.
- Dose adjustments may be necessary for patients with kidney impairment.
- Common side effects include drowsiness, dizziness, and cognitive effects, and patients should maintain adequate hydration as zonisamide can increase the risk of kidney stones.
Dosage Recommendations
- For adults with epilepsy, the usual maintenance dose ranges from 200-400 mg daily, taken once or twice daily, with a maximum recommended dose of 600 mg daily 3.
- For children, dosing is weight-based, usually starting at 1-2 mg/kg/day and gradually increasing to 4-8 mg/kg/day.
- When used for migraines or other off-label purposes like weight loss, lower doses are often prescribed, such as 50-200 mg/day 4.
Efficacy and Safety
- Zonisamide has been shown to be effective in reducing seizure frequency by at least 50% in patients with focal epilepsy, with a number needed to treat for an additional beneficial outcome of six 2.
- The medication has a moderate-quality evidence base for its use in focal epilepsy, with a significant association with adverse effects such as ataxia, somnolence, agitation, and anorexia 2.