Cebranopadol Efficacy and Safety in Diabetic Patients Suffering From Chronic Pain Caused by Damage to the Nerves

Inclusion Criteria: * written signed informed consent * type 1 or type 2 diabetes mellitus * clinical diagnosis of painful Diabetic Polyneuropathic Neuropathy (DPN) with symptoms and signs for at least 3 months * must require medication (e.g., non-opioids or opioids up to an equivalent dose of 160 mg oral morphine/day) for the treatment of pain due to DPN for at least 1 month prior to Visit 1 and must be dissatisfied with the current treatment (in terms of efficacy and/or tolerability). Medication for the treatment of pain due to DPN should be required on at least 4 of 7 consecutive days. * blood glucose to be controlled by a diet, oral anti-hyperglycemic medication, and/or insulin for at least 3 months prior. Glycosylated hemoglobin (HbA1C) should not be greater than 11% * baseline pain intensity score greater or equal to 5 on the 11-point Numerical Rating Scale (NRS) without intake of any analgesic at allocation. For each of the last 3 days prior to allocation of treatment, a 24 hour NRS score greater or equal to 4 is required * women of childbearing potential must have a negative urine pregnancy test at enrollment * using medically acceptable and highly effective methods of birth control (and willing to use them during the trial). Exclusion Criteria: * presence of other pain that could confound the painful Diabetic Polyneuropathy (DPN) assessments, e.g. pain due to nerve entrapment (tarsal tunnel syndrome, osteoarthritis of the knee etc), peripheral vascular disease, ra…