Zonisamide add-on for drug-resistant partial epilepsy.

Area of Science:

• Neurology
• Pharmacology
• Clinical Trials

Background:

• Up to 30% of epilepsy patients develop drug-resistant epilepsy, particularly those with partial seizures.
• Zonisamide is an antiepileptic agent evaluated for add-on treatment in refractory epilepsy.

Purpose of the Study:

• To evaluate the efficacy and safety of zonisamide as an add-on treatment for drug-resistant partial epilepsy.
• To assess seizure frequency reduction, treatment withdrawal, and adverse events associated with zonisamide therapy.

Main Methods:

• Systematic review of randomized placebo-controlled add-on trials of zonisamide.
• Searched Cochrane Epilepsy Group Specialized Register and contacted drug manufacturers and experts.
• Data extracted on seizure reduction, withdrawal rates, and adverse events; intention-to-treat analyses performed.

Main Results:

• Zonisamide (100-500 mg/day) significantly increased the likelihood of a 50% or greater seizure frequency reduction (RR 2.35, 95% CI 1.74 to 3.17).
• Higher zonisamide doses (300-500 mg/day) were associated with increased treatment withdrawal (RR 1.64, 95% CI 1.20 to 2.26).
• Significantly associated adverse effects included ataxia, dizziness, somnolence, agitation, and anorexia.

Conclusions:

• Zonisamide demonstrates efficacy as an add-on treatment for drug-resistant partial epilepsy.
• Minimum effective and maximum tolerated doses were not identified.
• Study duration was limited to 12 weeks, precluding conclusions on long-term effectiveness or use in monotherapy or other epilepsy types.