Inclusion Criteria:  aged 19 to 75 type 2 diabetes mellitus with HbA1c (Hemoglobin A1c) ≤ 10 % peripheral (eg. hands, feet) neuropathic pain (eg. abnormal sensations, numbness, pain, etc.) within 3 months (12 weeks) diagnosed with diabetic peripheral neuropathy (DPN) VAS pain score ≥ 40 mm written informed consent  Exclusion Criteria:  brittle diabetes mellitus ALT (Alanine Transaminase), AST (Aspartate Transaminase), CPK (Creatine Phosphokinase) level ≥ 3 times the upper limit of normal (UNL) or active liver disease severe renal impairment (eGFR (estimated glomerular filtration rate) < 60 mL/min/ 1.73m2) treated with antiepileptic drugs within 1 week at randomization other nervous system or neuropathic disorders that may affect pain evaluation oral drug administration is not possible, or hypersensitive or allergic to pregabalin, r-thioctic acid tromethamine, thioctic acid, and other excipients pregnant, lactating, or childbearing potential alcoholics, drug abusers, and patients who are difficult to participate in clinical trials due to psychological and emotional problems have participated in other clinical trials within 30 days at screening