To evaluate the efficacy and safety of oral Lacosamide as first add on treatment in subjects with uncontrolled partial-onset seizures after prior treatment with a monotherapy Antiepileptic Drug (AED) regimen compared to subjects who have received treatment with at least 2 AEDs.

The study consisted of 3 Periods: Period 1: a 1-week Screening Phase, Period 2: a 30-week Treatment Phase (consisting of a 6-week Titration Phase and a 24-week Maintenance Phase), and Period 3: a 3-week Taper/Safety Follow-Up Phase.

Inclusion Criteria:

Group 1:

• Subject has a diagnosis of epilepsy with simple partial seizures (motor component) and/or complex partial seizures with or without secondary generalization
• Currently taking adequate monotherapy (defined as a single Antiepileptic Drug (AED) for at least 28 days prior to Screening) and has no history of AED polytherapy. Prior use of rescue medication (short-term intermittent use) is acceptable
• Epilepsy diagnosis should be ≤24 months at the time of the Screening Visit
• The minimum allowed seizure frequency at any time during the 12 weeks prior to the Screening Visit is ≥3 partial-onset seizures

Group 2:

• Subject has a diagnosis of epilepsy with simple partial seizures (motor component) and/or complex partial seizures with or without secondary generalization
• Currently taking 1 to 3 AEDs, and has tried at least 2 prior AED treatment regimens (concurrently or sequentially)
• Epilepsy diagnosis should be ≥5 years at the time of the Screening Visit
• The minimum allowed seizure frequency during the 12 weeks prior to the Screening Visit is ≥1 partial-onset seizure per 28 days

Exclusion Criteria:

• Previous use of Lacosamide
• History of seizure disorder characterized primarily by isolated auras
• History of primary generalized seizures
• History of status epilepticus within last 12-months
• History of cluster seizures during the 12 week period prior to Visit 1
• Nonepileptic events, including pseudoseizures that could be confused with seizure
• Lifetime history of suicide attempt or suicidal ideation in the past 6 months
• Hypersensitivity to any component of Lacosamide
• History of drug or alcohol abuse
• History of an acute or subacutely progressive Central Nervous System (CNS) disease
• Undergone cranial surgery within the last year prior to study entry
• Concomitant treatment of Felbamate or previous Felbamate therapy within the last 6 months
• Prior or concomitant Vigabatrin use