A Trial to Investigate Safety and Efficacy of SPM927 in Painful Diabetic Neuropathy

Inclusion Criteria: * Subject has clinically diagnosed pain attributed to diabetic distal sensory motor polyneuropathy for 1-5 years and a diagnosis of diabetes mellitus (Type I or Type II). * Subjects must have at least moderate pain (mean pain intensity ≥ 4 out of 10 during the baseline week on Likert scale). * subjects must have good or fair diabetic control (Hgb A1c \< 10%) Exclusion Criteria: * Subject has other conditions that cause neuropathic pain at least as severe as the diabetic pain i.e. peripheral arterio-vascular disease. * Subject receives treatment for seizures. * Subject has had any amputations other than diabetically-related toe amputations. * Subject has major skin ulcers. * Subject has clinically significant ECG abnormalities. * Subject is expected to take within 7 days prior to randomization and during the study: TCAs, mexiletine hydrochloride, lidoderm patch, tramadol, AEDs, dextromethorphan, opioids, capsaicin, nonsteroidal anti-inflammatory drugs, acetaminophen / paracetamol, skeletal muscle relaxants, benzodiazepines, alpha-2-agonists (e.g. clonidine), drugs indicated for sleep disturbance (e. g. zolpidem tartrate, zaleplon) and over-the-counter medications with centrally acting properties. * Subject has laboratory values which are outside the normal range and judged by the investigator to be clinically significant. * At study entry, subject has liver function tests values (AST, ALT,alkaline phosphatase, total bilirubin and GGT) 2 times upper limit of normal. * subject has impaired renal function, i.e., creatinine clearance is lower than 60 mL/min.