Evaluation Phenobarbital as Adjunctive Therapy in Participants With Partial Onset Seizures

Inclusion Criteria: * participants from 17 to 70 years old; * history of Type I partial onset seizures (complex or simple with motor symptoms only); * participants must have had electroencephalogram (EEG), magnetic resonance imaging (MRI) or computed tomography (CT) with results consistent with diagnosis of partial-onset seizures; * participants having at least eight Type I partial onset seizures during 8-week baseline period; * participants being uncontrolled while treated by 1 to 3 permitted concomitant anti-epileptic drug (AED) and/or Vagus Nerve Stimulation (VNS); * participant has been on a stable dose of their current anti-epileptic treatment regime Exclusion Criteria: * currently taking phenobarbital or primidone; * currently taking felbamate or vigabatrin; * history of prior allergic reaction to phenobarbital; * history of psychogenic seizures; * history or presence of status epilepticus; * history or presence of seizures occurring only in clusters; * participant taking any drug with possible Central Nervous System (CNS) effects except if stable from 1 month prior Visit 1; * history of cerebrovascular accident (CVA) or transient ischemic attack (TIA); * presence of any sign suggesting rapidly progressing brain disorder or brain tumor; * presence of unstable arteriovenous malformations, meningiomas or other benign tumors; * history of porphyria; * presence of clinically significant findings on physical exam, vital signs, electrocardiogram (ECG) or safety lab assessments, including renal or hepatic insufficiency; * history of alcohol or drug abuse within the year prior to screening; * participant who is known to be non-compliant; * participant who is male or female who refuses to use an acceptable form of contraception; * female who is pregnant or lactating or intends to become pregnant; * participant who has taken part in any investigational device or product within 2 months prior to the screening visit