A Study to Compare Oxycodone/Naloxone Prolonged Release Against Codeine/Paracetamol in the Treatment of Moderate to Severe Chronic Low Back Pain or Pain Due to Osteoarthritis

This is a randomised, double-blind, double-dummy, parallel group, 12-week study to assess the efficacy and tolerability of oxycodone/naloxone compared to codeine/paracetamol tablets in the treatment of moderate to severe chronic low back pain or moderate to severe pain due to OA of the hip and /or knee. The screening period will be 3 - 7 days duration. If a subject meets all the screening criteria they may enter the Run-in Period. During the screening period subjects will continue to take their pre-study pain medication. The run-in period will be 7 - 14 days duration. During the run-in period subjects will continue to take their pre-study pain medication. Visit 3 will occur at the end of the Run-in Period (7-14 days after Visit 2). To qualify for entry into the treatment period of the study, subjects must have uncontrolled pain as shown by average daily pain scores of \>5 on 4 of the last 7 days of the run in period. Eligible subjects will be randomised to either oxycodone/naloxone or codeine/paracetamol tablets. Subjects will receive double-blind study medication for up to 12 weeks.