A Multicentre, Randomised, Double-Blind, Parallel Group Comparison Of The Efficacy And Safety Of Transdermal Buprenorphine (Norspan'registered trade mark' BTDS) And Placebo In Patients With Postherpetic Neuralgia.

INTERVENTION: Buprenorphine Transdermal Delivery System (patch applied to the skin), 5, 10, 20, 30, 40 micrograms per hour. Duration of treatment: maximum of 21 weeks CONDITION: Post Herpetic Neuralgia PRIMARY OUTCOME: Rate of response for pain relief, where response is defined as a 30% reduction in pain using the daily Numerical Rating Scale (NRS). Patients who withdraw will be classified as non‐responders. SECONDARY OUTCOME: Change from baseline in mean categorical scale score for pain intensity. Change from baseline in weekly NRS and categorical scores for continuous pain, paroxysmal pain and allodynia. Change in affective state as measured by Beck Depression Inventory (BDI II) Change in Health‐Related Quality of Life (QOL) as measured by SF‐36. Change in interference by pain in daily activities as measured by Brief Pain Inventory (BPI) Change in Short‐Form McGill Pain Questionnaire (SF‐MPQ) Clinician Global Impression of Change Scale (CGIC). Differences in total rescue medication usage between active and placebo treatment groups. Mean categorical scale score for pain relief . Mean reduction in pain intensity using the daily Numerical Rating Scale (NRS). Patient Global Impression of Change Scale (PGIC). INCLUSION CRITERIA: 1. Patients of either gender aged 18 years or older. 2. History of ongoing pain due to PHN of at least three months duration following initial Acute Herpes Zoster (AHZ) infection and rash healing, with pain intensity at screening visit of at least moderate intensity (NRS = 4/10). 3. Willingness to discontinue any current weak opioid analgesics (codeine‐containing, propoxyphene‐containing or tramadol) and any topical PHN therapies. 4. Patients receiving non‐opioid adjuvant analgesic medications (e.g. antidepressants, AEDs, mexiletine, clonidine) or NSAIDs / COX‐2 inhibitors must have a documented history of stable use over the previous three weeks with agreement to continue at a stable dosage for the duration of the trial. 5. Patients willing and able to participate in all aspects of the study, including initial medication weaning and cessation (if applicable), use of medication, completion of subjective evaluations, attending schedu