Assessment of Long-term Safety in Patients With Non-cancer-related Pain and Opioid-induced Constipation

Inclusion Criteria: * Provision of written informed consent prior to any study-specific procedures. * NEW PATIENTS ONLY: Self-reported active symptoms of OIC at screening (\<3 SBMs/week and experiencing \>1 reported symptom of hard/lumpy stools, straining, or sensation of incomplete evacuation/anorectal obstruction in at least 25% of the BMs over the previous 4 weeks); and Documented confirmed OIC (\<3 SBMs/week on average over the 2-week OIC confirmation period. * PATIENTS ENROLLING FROM OTHER NKTR-118 STUDIES: Receiving a stable maintenance opioid regimen consisting of a total daily dose of 30 mg to 1000 mg or oral morphine, or equianalgesic amount(s) of 1 or more opioid therapies. * FOR PATIENTS RANDOMIZED TO RECEIVE NKTR-118: Willingness to stop all laxatives and other bowel regimens including prune juice and herbal products throughout the 52-week treatment period, and to use only bisacodyl as rescue medication if BM has not occurred within at least 72 hours of the last recorded BM. Exclusion Criteria: * Patients receiving Opioid regimen for treatment of pain related to cancer. * History of cancer within 5 years from first study visit with the exception of basal cell cancer and squamous cell skin cancer. * Medical conditions and treatments associated with diarrhea, intermittent loose stools, or constipation. * Other issues related to the gastrointestinal tract that could impose a risk to the patient. * Pregnancy or lactation.