Zonisamide add-on therapy for focal epilepsy

Area of Science:

• Epilepsy research
• Clinical pharmacology
• Neurology

Background:

• Up to 30% of epilepsy cases develop drug-resistant epilepsy, particularly focal seizures.
• Zonisamide is an antiepileptic drug used in treatment regimens.
• This review updates previous Cochrane reviews on zonisamide's efficacy.

Purpose of the Study:

• To evaluate zonisamide's efficacy and tolerability as an add-on treatment for focal epilepsy.
• To assess outcomes in patients with focal epilepsy uncontrolled by existing antiepileptic drugs.

Main Methods:

• Systematic review of randomized controlled trials (RCTs).
• Searched Cochrane Register of Studies and MEDLINE (September 2019).
• Included 8 studies with 1636 participants; assessed risk of bias and certainty of evidence using GRADE.

Main Results:

• Zonisamide (300-500 mg/day) showed a 1.90 RR for at least 50% seizure reduction versus placebo (moderate certainty).
• Treatment withdrawal RR was 1.59 for zonisamide (300-500 mg/day) versus placebo (moderate certainty).
• Adverse effects included ataxia, somnolence, agitation, and anorexia.

Conclusions:

• Zonisamide is effective as add-on therapy for focal epilepsy, reducing seizure frequency by at least 50%.
• Minimum effective and maximum tolerated doses were not identified.
• Results are not applicable to monotherapy or other seizure types.