Comparing The Effect On Cognition Of Adjunctive Therapy With Zonisamide Versus Sodium Valproate

Zonisamide (Zonegran) and sodium valproate (Epilim) are both medicines approved to treat epilepsy. The purpose of this study is to find out the extent to which zonisamide may affect memory and concentration, compared to sodium valproate. This will be investigated using cognitive tests which are performed on a computer screen. Either zonisamide or sodium valproate will be added as a second medicine to the one patients are currently taking, carbamazepine (Tegretol), which will be continued throughout the study. It is planned that about 80 people across Europe will take part in this study. For the purpose of the study, patients will need to go to the study doctor's clinic 4 times and have 5 telephone calls. Involvement in the study might be as long as 20 weeks, but it could be as short as 12 weeks. The length of the study and number of visits will depend on whether patients have an accurate recording of previous seizures already, how many seizures they have during the study, and whether they decide to continue or to stop treatment after the study is completed. Adult subjects with a clinical diagnosis of non-symptomatic (i.e., idiopathic or unknown cause) localisation-related epilepsy, with partial onset seizures with or without secondary generalisation, who are receiving fixed dose carbamazepine as their only therapy or can be transferred to carbamazepine (as their only therapy) in the two months before the study baseline. Subjects must require addition of another anti-epileptic drug (AED) to their anti-epileptic therapy, either because they continue to have seizures (i.e., are not controlled), or because they wish to switch to another AED for other reasons (e.g., they tolerate another drug better).