Abstracts

RATIONALE: Zonisamide (Zonegran[reg]) is a unique antiepilepsy drug (AED) that is chemically classified as a sulfonamide. Its mechanism of action appears to be broad based and involves inhibition of voltage-sensitive sodium channels and T-type calcium channels. Zonisamide has been available in Japan for more than a decade and was approved in the United States in 2000 for adjunctive treatment of partial seizures in adults with epilepsy. To date, little information is available regarding the use of zonisamide in patients with absence seizures. The objective of this case-review study was to assess the efficacy and safety of zonisamide as adjunctive therapy in patients with absence seizures.
METHODS: Three female patients (aged 21, 11, and 51 years) with atypical or typical absence seizures had zonisamide added to their current AED regimen after their current regimens failed to produce an adequate therapeutic response and/or produced adverse events. Zonisamide was delivered twice daily at a dosage of 600 mg/d in 1 patient and 400 mg/d in 2 patients. Efficacy was assessed by normalization of electroencephalogram (EEG) readings and/or reduction in seizure frequency. Safety was assessed by examination of adverse events.
RESULTS: After initiation of zonisamide therapy, all patients exhibited improvement in seizure control. All patients have shown a decrease in seizure frequency, 1 of whom has been seizure free for 6 months. Additionally, zonisamide normalized EEG readings in 1 patient who had abnormal readings prior to zonisamide therapy. All 3 patients have been controlled with zonisamide alone or in combination with other AED(s). Zonisamide has been well tolerated in all 3 patients, and no adverse events associated with zonisamide have been reported.
CONCLUSIONS: All patients in this case review demonstrated decreased seizure frequency when zonisamide was added to their therapeutic regimen, and no adverse events associated with zonisamide have been reported. These results suggest that adjunctive therapy with zonisamide may be used to treat atypical and/or typical absence seizures that are inadequately controlled with other AEDs. It is hoped that these preliminary results will encourage further investigation of the use of zonisamide in patients with absence seizures.
(Disclosure: Honoraria - Elan Pharmaceuticals)