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.

Eligibility Criteria:
Inclusion Criteria:

* Participants with chronic pain due to painful diabetic neuropathy or postherpetic neuralgia continuing for at least 12 weeks before consent
* Participants with adjuvant analgesics (antidepressants, antiepileptics and diabetic peripheral neuropathy drugs) or non-opioid treatment and dissatisfied with current treatment (in sense of efficacy and/or safety) for at least consecutive 14 days during the 12 weeks before consent
* Participants have not experienced treatment with conventional opioids, except for the following cases: Short term use of opioid analgesics for treatment of post-operative acute pain more than 30 days before consent; and temporal use of codeine phosphate or dihydrocodeine phosphate for purposes other than pain relief (for example, for antitussive) more than 2 days before consent
* Mean pain intensity score of greater than or equal to 5 on an 11-point Numerical Rating Scale during 48 hours before consent and the Investigator or Sub-investigator considers that the participant should be treated with an opioid analgesic
* HbA1c within 4 weeks before consent less than or equal to 11percent (in participants with diabetic neuropathic pain)

Exclusion Criteria:

* Participants have been treated or treated with a monoamine oxidase inhibitor within 14 days before consent
* Current or a history of epilepsy or convulsive disorders or hypersensitivity to opioid analgesics
* Suggested of intracranial hypertension (for example, traumatic encephalopathy)
* Participants who have complicated condition with uncontrolled or clinically significant arrhythmia, or neuropsychiatric disorders
* Participants with moderately to severely impaired hepatic function, or severely impaired renal function