A Randomised, Double-blind, Double-dummy, Parallel-group Multicenter Study to Demonstrate Improvement in Symptoms of Constipation and Non-inferiority in Analgesic Efficacy in Subjects With Non-malignant or Malignant Pain That Require Around-the-clock Opioid Therapy Taking 50/25 - 80/40 mg Twice Daily as Oxycodone/Naloxone Prolonged Release (OXN PR) Tablets Compared to Subjects Taking 50 - 80 mg Twice Daily Oxycodone Prolonged Release (OxyPR) Tablets Alone

The study OXN3506 is a multicentre, multiple-dose, randomised, double-blind, double-dummy, active-controlled, parallel-group study in male and female subjects with non-malignant or malignant pain requiring opioids to assess analgesic efficacy and symptoms of constipation secondary to opioid treatment. Subjects will be randomised to two treatment groups and will be treated with OXN PR or OxyPR for up to 5 weeks. The study is composed of three phases, a pre-randomisation phase, a double-blind phase and an extension phase.