Efficacy and Safety of Adjunctive Zonisamide in Paediatric Partial Onset Seizures (CATZ Study)

This will be a double-blind, randomised, study comparing zonisamide with placebo: each arm will consist of 102 subjects. Zonisamide/placebo dosing will commence with a dose of 1 mg/kg. Further dose increases will occur at weekly intervals until a dose of 8 mg/kg is reached at the end of Week 8. In the event of dose limiting adverse events (AEs), during the eight week Titration Period, one down titration to a lower dose is permitted, this can happen at any point in the Titration Period. Subjects who require further down titration steps will be withdrawn from the study. During the Maintenance Period the dose of study medication must remain unchanged. Changes in concomitant AEDs are not permitted during the Screening, Titration or Maintenance Periods. This trial consists of the following periods: 1. Screening Period (duration four weeks): once the Screening Visit has been performed, a seizure diary will be maintained to document the baseline seizure frequency in the eight weeks between the Screening Visit and the Randomisation Visit. 2. Titration Period (duration four weeks): during this period, zonisamide/placebo dosing will commence with a dose of 1 mg/kg. Further dose increases will occur at one week intervals until a dose of 8 mg/kg is reached at Visit 6 (Week 8). In the event of dose limiting AEs during the Titration Period, one down titration step to the previous dose will be permitted. 3. Maintenance Period (duration 12 weeks): during this period, randomised subjects will be treated with the dose of zonisamide/placebo which they were receiving at Visit 6 (Week 8). No changes to the dose are allowed during this phase. Following the Maintenance Period subjects will have the opportunity to enter an open label extension study. This open label extension study will be the subject of a separate protocol and will not be discussed further at this time.