• Subject has experienced febrile seizures exclusively. The occurrence of febrile seizures in addition to partial onset seizures is not exclusionary • Subject is on a ketogenic diet that has either changed within the 4 weeks prior to Visit 1 or is expected to change during the study • Subject has creatinine clearance <30 mL/minute • Subject has a clinically relevant ECG abnormality, in the opinion of the investigator (eg, second or third degree heart block at rest or a corrected QT interval [QTc] >=450 ms) • Subject has a hemodynamically significant congenital heart disease • Subject has an arrhythmic heart condition requiring medical therapy • Subject has a known history of severe anaphylactic reaction secondary to medication intake or serious blood dyscrasias • Subject has nonepileptic events that could be confused with seizures. Subjects may be included if epileptic events can be clearly distinguished and the frequency meets the study inclusion criteria • Subject has a current diagnosis of Lennox-Gastaut syndrome, epilepsia partialis continua, primary generalized epilepsy, Dravet Syndorme, or seizures that are not of partial-onset origin • Subject has a history of generalized convulsive status epilepticus <=2 months prior to Screening (Visit 1) • Subject has been treated with felbamate and has experienced any serious toxicity issues (defined as liver failure, aplastic anemia) with this treatment. Subjects treated with felbamate for <12 months are excluded. Subjects treated with felbamate for >=12 months prior to Visit 1 and who have not experienced serious toxicity issues are eligible • Subject has an acute or subacutely progressive central nervous system disease. Subject has epilepsy secondary to a progressing cerebral disease or any other progressively neurodegenerative disease (malignant brain tumor or Rasmussen Syndrome) • Subject has a known cardiac sodium channelopathy, such as Brugada syndrome