A 12-week Extension of the Phase III Study (D3820C00004) to Assess the Effect and Safety of NKTR-118 in Patients With Non-cancer-related Pain and Opioid-induced Constipation

Inclusion Criteria: * Must have completed the 12-week study D3820C00004 through Visit 8. * Provision of written informed consent prior to any study-specific procedures. * Men and women who were between the ages of \>18 and \<85 years at the time of the screening visit for study D3820C00004. * Continuing to receive a stable maintenance opioid regimen consisting of a total daily dose of 30 mg to 1000 mg of oral morphine, or equianalgesic amount(s) of 1 or more other opioid therapies. * Willingness to continue abstinence from all laxatives and other bowel regimens including prune juice and herbal products throughout this additional 12-week treatment period, and to use only bisacodyl as rescue medication if a bowel movement (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 the screening visit of study D3820C00004 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 risk to the patient. * Pregnancy or lactation.