A Study to Evaluate the Safety and Tolerability and Explore the Efficacy of Zonisamide as add-on Therapy in Elderly Patients With Refractory Partial Seizures

Key Inclusion Criteria: 1. Capable of maintaining a seizure daily diary or who have access to a caregiver who is prepared to complete this on the patient's behalf. 2. Able to complete the questionnaires used in this study. 3. Localization related epilepsy, with simple and/or complex partial seizures with or without secondary generalized seizures as defined by the International League Against Epilepsy (ILAE) criteria. 4. Have at least one well documented seizure in the 4 weeks preceding the Randomisation Visit (Visit 2) and are deemed to require additional AED medication. 5. Receiving at least one, but not more than two other marketed AEDs as concomitant medication, and the dosage should be stable for at least four weeks before the Screening Visit. Key Exclusion Criteria: 1. Seizures attributed to metabolic causes (e.g., electrolyte disturbances, hyperglycaemia). 2. Seizures which could be attributed to use of a drug. 3. Presence of primary generalised epilepsies or seizures, such as absences, myoclonic epilepsies, Lennox-Gastaut syndrome. 4. A history of eating disorders or a body weight below 40 kg. 5. A history of blood dyscrasias. 6. A history of renal stones or having risk factors for nephrolithiasis such as a family history of nephrolithiasis or hypercalciuria. 7. An increased risk factor for rhabdomyolysis such as uncontrolled hypothyroidism, personal or family history of muscle disorders. 8. Taking concomitant medication associated with nephrolithiasis and medications increasing the risk of rhabdomyolysis. 9. Taking rifampicin or drugs with anticholinergic effects. 10. Taking carbonic anhydrase inhibitors or topiramate. 11. A history of pancreatitis. 12. A history of Stevens Johnson Syndrome. 13. Elevated levels of serum creatinine \>165 Umol, or known severe hepatic impairment to the extent that the protocol dose titration schedule cannot be followed.