Post marketing surveillance on the use of zonisamide for epilepsy in the Philippines: A preliminary report

ABSTRACT

The objective of the study is to monitor on a wide population base the safety and efficacy of zonisamide in patients with partial, generalized, and combined seizures. This is an open label, descriptive, post-marketing surveillance preliminary report that includes the data obtained from October 2008 to May 2010 of a four-year study. The study included 516 patients allocated to either zonisamide monotherapy or zonisamide add-on therapy, with efficacy and safety assessed monthly for three months. For adult patients, a maximum oral dose of 600 mg per day was allowed while a maximum dose of 12 mg/kg/day of zonisamide was allowed for pediatric patients. Efficacy measures were the proportion of responders and percentage change in seizure frequency from baseline. 321 of the 516 patients were included in the efficacy analysis. The responder rates were 53.27%, 80.37%, and 92.52% after the 1st month, 2nd month, and 3rd month of treatment respectively. The use of zonisamide led to seizure-reduction rates of 45.74%, 68.43%, & 82.85% during the 1st, 2nd, & 3rd month of use respectively. Safety analysis was done on all the 516 subjects. Adverse events were mostly mild and observed in 6.78% of patients. No serious adverse events were encountered. 7 subjects (1.4%) discontinued taking zonisamide because of increased seizure frequency in 4 patients, and 1 patient each due to absence of effect on seizure-control, rashes, and thrombocytopenia. All the rest continued taking zonisamide.