• Average Area Under the Curve Minus Baseline (AAUCMB) of pain relief, as measured by Visual Analogue Scale (VAS) scores for daily pain during the treatment period (6 weeks)
  

• SF-36 Quality of Life Questionnaire (QoL) and WOMAC questionnaire on Days 1 and 43 and at end of tapering-off period; adverse events throughout study
  

Chronic, non-cancer pain may result from injury or illness, such as osteoarthritis or rheumatoid arthritis, which causes suffering and a reduction in the quality of life. Opioids, such as fentanyl, are beneficial as potent pain-relieving drugs in patients with continuous pain. This is double-blind, parallel-group, placebo-controlled study to compare pain relief, and the effect on safety, functionality, and quality of life during treatment with fentanyl administered through the skin via adhesive patches ("transdermal system") with therapy with placebo in patients with osteoarthritis (OA). Specifically, patients with moderate to severe pain induced by osteoarthritis and for whom treatment with traditional pain medication (according to the World Health Organization [WHO] pain ladder, up to and including weak opioids) has failed to provide adequate pain relief, are eligible to enroll. After screening, patients enter a 1-week Run-In period, in which prior treatment with weak opioids, with or without non-opioid pain medication, continues. After this period, patients with moderate to severe pain are randomized to the fentanyl adhesive patch or placebo during the Double-Blind (Treatment) phase for 6 weeks. All patients, including those who discontinue or withdraw from the study, enter the Tapering-Off period, during which the medication is reduced gradually. Assessments of effectiveness include: Pain relief, determined with a Visual Analogue Scale (VAS) by means of an electronic pain diary updated by the patient at least twice daily; functionality, assessed by the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index; and quality of life, measured by the SF-36 Quality of Life Questionnaire. Safety assessments include identification of possible withdrawal symptoms at the end of the Tapering-Off period, measurement of vital signs at stated intervals, and incidence of adverse events throughout the study. The study hypothesis is that patients with osteoarthritis of the hip or knee whose pain is not adequately controlled by other pain-relieving medications will show an improvement in pain control after treatment with the fentanyl transdermal system. Fentanyl patches to deliver 25 micrograms/hour to 100 micrograms/hour, changed every 3 days, for 6 weeks; doses may be adjusted for adequate pain control; anti-nausea tablets (Metoclopramide, 10 milligrams[mg], and paracetamol tablets (500 mg; maximum 4 grams/day) as supplementary pain control