Efficacy of Oxycodone/Naloxone(OXN), Versus Oxycodone (OXY), for the Reduction of Intensity of Opioid-induced Constipation in Pain Patients

Inclusion criteria 1. Male or female patient aged 18 years or older. 2. With cancer pain or non-cancer pain such as chronic low back pain, osteoarthritis or other. 3. Either currently receiving a WHO step II opioid and requiring the initiation of a WHO step III opioid (due to a lack of efficacy of the step II opioid) expected to last 28 days or more, or currently receiving a WHO step III opioid expected to last further 28 days or more. 4. Having opioid-related constipation defined by either a KESS score ≥ 9 or the current use of laxatives (at least 3 times per week). 5. Able, in the opinion of the Investigator, to comply with the study protocol. 6. Women of childbearing potential must have a negative urine pregnancy test result at inclusion (test under supervision of the investigator) and use an effective birth control method. Women of non-childbearing potential must be postmenopausal or surgically sterile (hysterectomy and/or bilateral oophorectomy). 7. Having received oral and written information about the study protocol and signed a written, informed consent to participate. Exclusion criteria 1. Pregnancy or breastfeeding. 2. Known contraindication or hypersensitivity to oxycodone, naloxone, bisacodyl, any chemically close substance, and ingredients. 3. Clinically significant impairment of cardiovascular, respiratory, liver or kidney function disease, as determined by medical history, clinical laboratory tests, ECG results, and physical examination, that in the opinion of the Investigator may present a risk upon exposure to the study medication. 4. Known or suspected unstable brain or spinal cord metastases that may require changes in steroid treatment throughout the duration of the study. 5. Increased intracranial pressure. 6. Evidence of clinically significant gastrointestinal disease (e.g., paralytic ileus, peritoneal carcinosis), significant structural abnormalities of the gastrointestinal tract (e.g., scarring, obstruction etc) either related or not related to the underlying cancer or disease progression. 7. Rheumatoid arthritis, as co-medication may have an impact on the study results, especially if co-medication is not stable within the study. 8. Surgery completed prior to the start of the study, or planned surgery during the study that would influence pain or bowel function during the study or preclude completion of the study. 9. Cyclic chemotherapy in the two weeks before inclusion or planned during the study that has shown in the past to influence bowel function. Patients having their first cycle of chemotherapy during the 2 weeks before the inclusion visit or during the study they should not be included in the study. 10. Radiotherapy that, in the investigators opinion, would influence bowel function or pain during the study. 11. Treatment with an opioid receptor antagonist in the month preceding inclusion. 12. History of alcohol, opioid or other drug abuse. 13. Current treatment with another psychoactive drug that, in the opinion of the Investigator, may present a risk when associated with an opioid. 14. Any somatic or psychic condition that, in the opinion of the Investigator, may compromise the ability of the patient to understand and comply with the study protocol or to provide informed consent to participate. 15. Patient who participated in a clinical research involving a new chemical entity or an experimental drug within 30 days of study entry. Concurrent enrolment in another clinical trial is not permitted unless the sole purpose of the other trial at the time of the OXN3505 inclusion visit is for long-term follow-up/survival data.