Eslicarbazepine Acetate as Therapy in Diabetic Neuropathic Pain

Inclusion Criteria: * Male and female outpatients aged 18 years or older. Female subjects are of nonchildbearing potential, defined as surgical sterilization (hysterectomy or bilateral oophorectomy or tubal ligation) or at least 2 years postmenopausal (spontaneous amenorrhea for at least 24 months before Visit 1), or if of childbearing potential, subjects agree to use a medically acceptable nonhormonal method of contraception. * Diagnosis of Type 1 or Type 2 diabetes mellitus. * Pain due to bilateral peripheral polyneuropathy caused by Type 1 or Type 2 diabetes mellitus. * Have stable glycemic control, as assessed by the investigator, and have glycosylated hemoglobin proportion of less or equal than 11% before randomization. * A mean score between 4.0 and 9.0, inclusive, on the 24 hour average pain intensity assessment and Visit 3 (ie, 5 of 7 days, 6 of 8 days, 7 of 9 days, or 7 of 10 days). * Compliance with patient diary completion. * If not used to treat DNP, subjects are permitted to take nonsteroidal anti inflammatory drugs and selective serotonin reuptake inhibitors if they were kept on a stable dose for 1 month prior to Screening and are foreseen to remain stable throughout the study. * Competent and able to freely give own informed consent. * Female subjects of childbearing potential, who are not currently breastfeeding, must have a negative serum pregnancy test at Visit 1. Exclusion Criteria: * Historical exposure to drugs known to cause neuropathy. * Significant skin lesions (active infection, ulcer, etc). * Peripheral vascular disease with a history of amputation, except amputation of toes. * Known intolerance to ESL or to other carboxamide derivatives (eg, carbamazepine or oxcarbazepine) or frequent or severe allergic reactions with multiple medications. * Subjects who previously participated in a clinical study with ESL. * Major psychiatric disorders. * Serious or unstable disease that could compromise participation cause hospitalization during the study. * Second or third degree atrioventricular blockade not corrected with a pacemaker or any clinically significant abnormality in the 12 lead electrocardiogram as determined by the investigator. * Subjects taking the following drug classes and individual drugs are excluded: benzodiazepines (except short half life sleep agents), skeletal muscle relaxants, orally administered steroids, capsaicin, mexiletine, centrally acting analgesics (dextromethorphan, tramadol), opiates, topical lidocaine, anticonvulsants, tricyclic antidepressants, and serotonin norepinephrine reuptake inhibitors. These drugs require a minimum washout period of at least 5 times the half life and should be tapered appropriately using product label instructions as a guide. * Relevant clinical laboratory abnormality that, in the investigator's opinion, can compromise the subject's safety. * History of drug abuse or dependence (drug categories defined by DSM IV) within the past year, excluding nicotine and caffeine. * Subjects who, in the previous 30 days, received treatment with a drug that had not received regulatory approval for any indication at the time of study entry. * History of recurrent epileptic seizures except febrile seizures. * History of severe gastroparesis or gastric bypass surgery. * Neurolytic treatment for DNP. * Injected anesthetics or steroid use within 30 days of Visit 1. * Malignancy within past 2 years. * History of chronic hepatitis B or C within the past 3 months or human immunodeficiency virus infection.