Efficacy and Safety of Low-Dose Duloxetine Plus Alpha-Lipoic Acid Versus Standard-Dose Duloxetine in Painful Diabetic Peripheral Neuropathy

Inclusion Criteria: * Age ≥18 years. * Diagnosed case of diabetes mellitus. * Diabetic peripheral neuropathy diagnosed clinically according to the Toronto Clinical Neuropathy Score (TCNS) criteria with a TCNS score ≥6, with painful neuropathy confirmed using the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) Pain Scale with a score ≥12. * Duration of neuropathic symptoms ≥3 months. * Baseline Numerical Rating Scale (NRS) pain score ≥4. * Willingness to participate in the study and provide written informed consent. Exclusion Criteria: * Pain attributable to causes other than diabetic peripheral neuropathy, such as peripheral arterial disease (ischaemic pain), osteoarthritis, inflammatory arthritis, phantom limb pain, radiculopathy, or other chronic pain disorders. * Known vitamin B12 deficiency, hypothyroidism, chronic alcohol use, hereditary neuropathy, chemotherapy-induced neuropathy, HIV infection, or connective tissue disease. * Chronic kidney disease (CKD) stage ≥4. * Chronic liver disease or significant hepatic impairment (ALT \>3 times the upper normal limit). * Use of antidepressants, antiepileptic drugs, sedatives, antipsychotic drugs, or opioids within the preceding 4 weeks. * Pregnancy or lactation, or women planning pregnancy during the study period. * Known hypersensitivity or contraindication to duloxetine or alpha-lipoic acid. * Major depressive disorder as assessed by the Patient Health Questionnaire-9 (PHQ-9), cognitive impairment (MMSE \<24), active malignancy, or any serious medical condition that, in the opinion of the investigator, may interfere with study participation, treatment adherence, or outcome assessment.