A Confirmatory Study of Fentanyl in Participants With Post-herpetic Neuralgia, Complex Regional Pain Syndrome or Postoperative Pain Syndrome

The purpose of this study is to evaluate the efficacy and safety of fentanyl in opioid-naive participants with post-herpetic neuralgia, complex regional pain syndrome or post-operative pain syndrome who cannot obtain a sufficient analgesic effect by the treatment of non-opioid analgesics (drug used to control pain).

This is a multi-center (conducted in more than one center), double-blind (neither the participant nor the physician knows the assigned study drug), randomized (participants assigned study drug by chance), withdrawal study in opioid-naive participants with post-herpetic neuralgia (intense, typically intermittent pain along the course of a nerve caused by the varicella zoster virus), complex regional pain syndrome or post-operative pain syndrome. The study will consist of titration period (10-29 days) and double-blind period (12 weeks) and the visits will include Day 5-7, 8, 15, 22, 29 in titration period and Day 2-4, 8, 15, 22, 29, 43, 57, 71 and 85 in double-blind period. All the eligible participants will receive one-day adhesive transdermal patch (patch containing a drug that is put on the skin so the drug will enter the body through the skin) of either fentanyl at the dose ranging from 12.5 to 50 microgram/hour or matching placebo. Efficacy will be evaluated primarily by time to withdrawal due to insufficient analgesic efficacy. Participants' safety will be monitored throughout the study.

Eligibility Criteria:
Inclusion Criteria:

* Participants whose pain because of post-herpetic neuralgia, Complex Regional Pain Syndrome (CRPS) or post-operative pain syndrome is continuing for at least 12 weeks prior to informed consent
* Participants who are continuously taking a non-opioid analgesic at the normal highest dose or more for at least 14 consecutive days prior to informed consent, or at a certain dose (except the use on an as-needed base) on consecutive days or participants who are continuously taking an analgesic adjuvant with a certain dosage and administration (except the use on an as-needed base) for at least 14 consecutive days prior to informed consent
* Participants showing insufficient therapeutic efficacy of the non-opioid analgesic currently being used, and to requiring a continuous opioid analgesic as per the Investigator or Sub-investigator
* Participants with an average pain intensity of 50 millimeter or more on the Visual Analog Scale in 24-hour daily living prior to informed consent
* Participants who can be hospitalized to the 4th day after the initiation of titration period

Exclusion Criteria:

* Participants who had an operation that may affect the assessment within 30 days before informed consent
* Participants whose main cause of the pain to be assessed is considered attributable to psychogenic pain (physical pain that is caused, increased, or prolonged by mental, emotional, or behavioral factors)
* Participants with asthma, bradyarrhythmia (slow irregular heart beat) and severe respiratory function disorders
* Participants complicated with hepatic dysfunction such as fulminant hepatitis (inflammation of the liver) and liver cirrhosis (serious liver disorder in which connective tissue replaces normal liver tissue, and liver failure often occurs), or renal impairment such as nephritic syndrome, acute renal failure, and chronic renal failure
* Participants with a history of hypersensitivity to fentanyl and other opioid analgesics