Abstracts

Zonisamide (ZNS) is a broad-spectrum antiepileptic drug (AED) that was approved in the United States in the year 2000 as adjunctive treatment for partial seizures with or without secondary generalization in adults. It is a sulfonamide that acts via different mechanisms including blockage of voltage-dependent sodium, and T-type calcium channels. In addition, it has the ability to bind to GABA receptors. The objective of this study is to assess the efficacy and tolerability of ZNS in adults with intractable seizures (IS).
A retrospective chart review was performed for 20 adult patients with IS who had received ZNS as adjunctive treatment over the past three years.
The mean age of patients when ZNS was initiated was 35.8 (age ranged between 19 and 55). 17 patients had partial onset seizures (PS), while 3 had generalized onset seizures (GS). Of the 20 patients, 9 (45%) experienced [ge] 50% reduction in seizure frequency including all 3 patients with GS. Two of the 9 patients became seizure free, one of whom had GS. All patients were started on a daily dose of 100mg. The mean maintenance dose used in the 9 patients who improved was 422.2 mg. ZNS was added to 3 AEDs in 3 patients, 2 AEDs in 2 patients, and one AED in 4 patients. Three patients had a Vagal Nerve Stimulator.
Eleven patients discontinued the drug, 5 due to lack of efficacy, and 6 due to adverse events (AEs). The AEs included lethargy (3), dizziness (1), and skin rash (2).
This study shows ZNS to be both effective and safe when used as adjunctive therapy for intractable seizures in adults. Further study is warranted to confirm these findings, which are especially promising in patients with generalized onset seizures.