Efficacy, tolerability, and retention rates of zonisamide in older adult patients with focal-onset epilepsy: Experiences from two tertiary epilepsy centers.

Objective: The objective of this study was to evaluate the efficacy, tolerability, and retention rates for zonisamide (ZNS) in older adult patients with focal-onset epilepsy.

Patients And Methods: Chart reviews of patients aged 60years and older with focal-onset epilepsy treated with ZNS in two tertiary epilepsy centers were analyzed retrospectively.

Results: Eighty-five patients (41 males, 44 females) aged over 60years (range: 60-81) with focal-onset epilepsy treated with ZNS were identified; 55.3% of the patients (n=47) were on monotherapy. The median and average doses of ZNS doses were 200mg/day (range: 100-400) and 212.9±84.2mg/day, respectively. With ZNS treatment, 67.1% of the patients (n=57) were seizure-free for a median of 28months (range: 10-56) whereas 20% (n=17) of the patients had seizures that were unresponsive to ZNS treatment. Best seizure control was achieved in patients with poststroke epilepsy; seizure freedom was 80% in this subgroup. Overall retention rate was found to be 83.5%. There was no significant relation between receiving poly- or monotherapy and discontinuation of ZNS (p=0.18). Thirty-two of the patients (37.6%) lost weight. Median weight loss was 8kg (range: 2-16). There was no significant correlation between weight loss and the administered doses of ZNS (r=0.34; p=0.12).

Conclusion: Despite limitations due to the retrospective design of the study, the results show that ZNS is a well-retained drug with high efficacy in older adult patients with epilepsy.