The purpose of this study is to determine the efficacy of BIA 2 093 in the treatment of epileptic patients with refractory simple or complex partial seizures with or without secondary generalization.

This clinical trial was performed as a multicentre, add-on, double-blind, randomised, placebo-controlled, phase II study. During the double-blind treatment phase (12 weeks) patients were assigned to three treatment groups receiving BIA 2 093 once daily (ODG - once-daily group), BIA 2 093 twice daily (TDG - twice-daily group) or placebo (PLG - placebo group), respectively. Daily doses of BIA 2 093 were increased at four-weekly periods (400 mg, 800 mg and 1200 mg).

On completion of the 12-week double-blind treatment period, a 1-week tapering period was scheduled.

Inclusion Criteria:

• Male and female patients aged 18-65 years
• Patients with simple or complex partial seizures with or without secondary generalization since at least one year prior to randomisation visit
• At least 4 seizures per month within the last 2 months prior to randomisation
• Stable dose regimen of a maximum of two of the following AEDs: phenytoin, valproate, primidone, phenobarbital, lamotrigine, gabapentin, topiramate, clonazepam, during 2 months prior to randomisation
• Electroencephalogram (EEG) findings not contradicting the epilepsy diagnosis (e.g., primarily generalized epilepsy)
• Written informed consent.

Exclusion Criteria:

• Patient with nervus vagus stimulation
• Patient with primarily generalized seizures
• Known progressive neurological disturbance
• A history of status epilepticus within the past 3 months
• Seizure of non-epileptic origin
• Restricted legal competence and incapability to follow trial instructions
• Major psychiatric disorders
• Concurrent drug therapy with monoamine oxidase inhibitors or calcium channel blockers
• Need of excluded concomitant medication (see section 9.4.6.2)
• Use of oxcarbazepine or carbamazepine during the last 6 months before the randomisation visit
• Known hypersensitivity to oxcarbazepine or carbamazepine, or its metabolites
• Abuse of alcohol, drugs or medications
• History of relevant cardiac, renal, hepatic, endocrine, gastrointestinal, metabolic, hematologic or oncology disorders
• Second- or third-degree atrioventricular block not corrected with a pacemaker
• Relevant laboratory abnormalities (e.g., Na+< 130 mmol/L, alanine (ALT) or aspartate (AST) transaminase >2.0 times the upper limit of normal, white blood cell (WBC) count <3000 cells/mm3)
• Pregnancy, nursing or inadequate contraception in women of childbearing age (oral contraception should be combined with a barrier method)
• Participation in other clinical trials within the last 2 months
• History of non-compliance.