Zonisamide in children with focal epileptic seizures: results of a prospective multicenter observational study (October 2025–June 2026)

Background. Management of pediatric epilepsy remains a critical challenge due to the insufficient efficacy of first-line therapies, adverse effects, and constraints within current clinical guidelines.

Aim. To evaluate the efficacy of zonisamide and its impact on the frequency, severity, and types of seizures after 3 and 6 months of therapy. Additionally, to assess the safety and tolerability of zonisamide treatment, the incidence and nature of adverse events (AE), and its impact on body weight and cognitive functions using the pediatric EpiTrack test after 3 and 6 months of therapy.

Materials and methods. A multicenter study was conducted involving 35 physicians from various regions of the Russian Federation. The study enrolled 115 patients aged 6 to 17 years inclusive (mean age: 9.95 years), including 52 % boys, with a confirmed diagnosis of focal epilepsy. Zonisamide (Zonegran, JSC “Firma EUROSERVICE”, Russia) was prescribed according to the manufacturer’s instructions as adjunctive therapy for focal epilepsy with or without secondary generalization. Epileptic syndromes for which zonisamide was initiated included: self-limited focal epilepsies of childhood, structural focal epilepsies, structural variant of Lennox–Gastaut syndrome, and genetic epilepsies. Individual patients could exhibit a combination of multiple focal seizure types. Zonisamide was administered as add-on therapy at a mean daily dose of 4.6 mg / kg. After 3 months, 16 patients dropped out of the study due to non-compliance with the study protocol. During these first 3 months, no patients discontinued the study due to zonisamide withdrawal. A total of 99 patients continued the study. After the subsequent 3 months (i.e., 6 months from the baseline), an additional 5 patients dropped out; thus, 94 patients completed the study. Among these 5 remaining dropouts, only 2 patients discontinued due to zonisamide withdrawal, while the others dropped out due to protocol violations. Consequently, the baseline cohort consisted of 115 patients, with a total of 21 patients dropping out (19 due to protocol violations and 2 due to zonisamide discontinuation).

Results. Efficacy of zonisamide treatment was observed in 83 out of 94 patients. The highest rate of complete seizure control was recorded in the early adjunctive therapy group, where zonisamide was prescribed as the second add-on medication. Five patients developed AE that required treatment discontinuation. In the remaining patients, AE occurred during the titration period and were deemed acceptable (decreased body weight and appetite in overweight patients). Concurrently, a reduction in migraine frequency was reported in one patient, a decrease in tic severity in one patient, and an improvement in hyperactive behavior.

Conclusion. Zonisamide demonstrates high efficacy and favorable tolerability. The incidence of AE is comparable to that of other modern antiepileptic drugs.