Study for Safety and Effectiveness of RWJ-333369 (Carsibamate) for the Treatment of Diabetic Peripheral Neuropathy (DPN).

Inclusion Criteria: * Have diabetes mellitus (Type 1 or 2) for longer than 1 year * Have clinical evidence of diabetic peripheral neuropathy in the lower extremities for 1 to 5 years before study entry * Experienced lower extremity pain due to diabetic peripheral neuropathy on nearly a daily basis for the previous 3 months * Have hemoglobin A1c levels less than or equal to 10% * Have a stable diabetic treatment regimen, including oral medications for controlling diabetes, insulin, or diet for 3 months before screening * Women must be postmenopausal for at least 2 years, sexually abstinent, or if sexually active, be practicing an effective method of birth control, and have a negative serum pregnancy test at screening. Exclusion Criteria: * History of a poor response to 3 or more medications for diabetic peripheral neuropathy (DPN), with poor response is defined as treatment with medications in the following categories of therapy for at least 1 month at therapeutic dosages without at least moderate improvement, as judged by the study doctor: antiepileptic drugs, tricyclic antidepressants, serotonin norepinephrine reuptake inhibitors (SNRIs), opioid analgesics, or lidocaine patch * currently taking tricyclic antidepressants, Coumadin (warfarin), or continued treatment with an antiepileptic drug for any indication, Note: If taking these medications, to be eligible for the study, they must be tapered and discontinued * Prior neurolytic treatment (destruction of nerves by the application of chemicals, heat, or cold), intrathecal pumps, or spinal cord stimulators for DPN pain * Use of herbal creams or ointments for pain relief within 48 hours, capsaicin within 6 months, or systemic corticosteroids within 3 months before the baseline period * Prior exposure to RWJ-333369 (carisbamate).