A Phase 2 Study of Tapentadol Extended-Release (JNS024ER) ) in Japanese Participants With Chronic Pain Due to Diabetic Neuropathic Pain or Postherpetic Neuralgia

The purpose of this study is to investigate the efficacy and safety of tapentadol extended-release (ER) tablets in Japanese participants with moderate to severe chronic (lasting a long time) pain due to painful diabetic peripheral neuropathy (pain in the extremities related to diabetes-induced nerve damage) or postherpetic neuralgia (pain lasting after condition has healed).

This is a randomized (study drug assigned by chance), multi-center (when more than one hospital or medical school team works on a medical research study), double-blind (neither physician nor participant knows the name of the assigned drug), placebo-control (participants are randomly assigned to a test treatment or to an identical-appearing treatment that does not contain the test drug), and parallel-group (each group of participant will be treated at the same time) comparison study in Japanese participants with chronic pain due to painful diabetic peripheral neuropathy or postherpetic neuralgia. The duration of study will be 14 weeks. The study consists of 3 parts: Screening (1 Week before study commences on Day 1); Treatment (12 weeks and will include titration period \[from the initiation of the study treatment to determination of the individual's maintenance dose\] and maintenance period \[from completion of the titration period up to12 week\]); and Follow-up (1 Week). Tapentadol hydrochloride ER oral tablet or matching placebo will be administered twice daily for 12 weeks. Efficacy of the participants will primarily be evaluated through Numerical Rating Scale (NRS). Participants' safety will be monitored throughout the study.