Optimisation of Hydromorphone - Naloxone Ratio for the Treatment of Pain

Inclusion Criteria: 1. Male or female subjects at least 18 years with a history of non-cancer or cancer pain that requires around-the-clock opioid therapy (8, 24 or 48 mg hydromorphone PR per day for the duration of the study). 2. Subjects with constipation caused or aggravated by opioids 3. Subjects must be willing to discontinue their current opioid analgesic routine, and . 4. current laxative regimen Exclusion Criteria: 1. Chronic or intermittent pain that results from Fibromyalgia or Rheumatoid Arthritis. 2. Subjects presently taking, or who have taken, naloxone \<=30 days prior to the start of the Screening Period. 3. Subjects suffering from diarrhoea. 4. Abnormal liver or kidney function.