A Long-term Safety Study With Tapentadol ER and Oxycodone CR in Patients With Moderate to Severe Pain Due to Chronic, Painful Diabetic Peripheral Neuropathy (DPN)

This is a randomized, open-label, active-controlled, multicenter study evaluating the safety profile of orally administered tapentadol, using the extended release tamper-resistant formulation (TRF), at dosages of 100 to 250 mg twice daily in patients with moderate to severe pain due to chronic, painful DPN. The study consists of 1) a 13-day screening period, a 3-7-day washout period (where patients are to stop taking their pain medication), a 1-day pretitration pain-intensity evaluation period (where patients will record their 24-hour pain intensity), and a 3-week, open-label titration period (patients will receive either tapentadol ER or oxycodone CR study drug in a 3 to 1 ratio), 2) a 49-week, open-label maintenance phase, and 3) a posttreatment phase of approximately 10 to 14 days. The study will evaluate the safety and tolerability of orally administered tapentadol ER by vital signs, physical examinations, clinical laboratory tests, 12-lead electrocardiograms (ECGs), opioid withdrawal scales, assessment of patient-reported constipation, standardized neurologic examinations and monitoring of adverse events. Assessments of pain relief include the pain intensity numerical rating scale, and patient global impression of change scale (PGIC). The total duration of study drug treatment for each patient will be approximately 52 weeks. Titrate tapentadol ER 50 mg twice daily or oxycodone CR 10 mg twice daily to patient's optimal dose ranging between 100 mg and 250 mg twice daily or 20 and 50 mg twice daily, respectively. All doses of study medication will be taken orally with or without food for a maximum timeframe of 52 weeks.