Long Term Safety and Tolerability Study in Approximately 350 Subjects With Moderate to Severe Chronic, Non-malignant Pain

Inclusion Criteria: * Males and Females between 21 and 75 years of age * Females must be of non-child bearing potential or practicing birth control * Moderate to severe mechanical low back pain OR moderate to severe OA of the hip or knee pain * Require medicine for pain the majority of days in the previous 3 months, AND for at least 4 days per week, during the previous 4 weeks. * Pain is not controlled with non-opioid analgesics or is contraindicated due to side effects and/or currently receiving opioid therapy equivalent to 40 mg/day of morphine or less Exclusion Criteria: * Pregnant and/or breastfeeding females or females planning to become pregnant during the course of the study * Incapacitated, bedridden, or confined to a wheelchair permitting little or no self-care * Injury to the index joint or lower back within 3 months of study * History of any of the following: * Major surgery to the lower back within the last 5 years OR * Joint replacement/reconstruction to the index joint OR * Arthroscopic or open surgery to the index joint within the last year OR * Any surgery within 3 months of study * Osteoporotic compression fracture, traumatic vertebral fracture or invasive intervention for low back pain within the last year. * Abnormal neurological exam, or lower extremity symptoms characteristic of neurogenic pain * History of inflammatory or infectious arthritis, tumors or infections of spinal cord, spinal stenosis, fibromyalgia or other chronic painful condition * Severe gastrointestinal narrowing * History of peritonitis, cystic fibrosis, chronic intestinal eudoobstruction, or Meckel's diverticulum. * Has received * Oral, intramuscular (IM), intravenous (IV) or non-index joint intra- articular corticosteroids within 1 month of study OR * Intra-articular corticosteroids at the index joint or epidural corticosteroids to the lower back region within 2 months of study, OR * Viscosupplementation therapy to index joint within 4 months of study * History of drug (licit or illicit) or alcohol abuse/addiction * Positive result for drugs of abuse at screening. * Chronic heavy drinker, consuming more than 4 alcoholic drinks per day. * History of malnutrition or starvation or is likely to fast for more than 4 consecutive days during the course of the study. * Medical condition or illness other than OA/CLBP, which is not well controlled * History of allergic reaction or a clinically significant sensitivity or intolerance to opioids and/or acetaminophen. * Newly diagnosed medical condition * Clinically significant infection/injury/illness within 1 month of study * Receiving systemic chemotherapy, or has an active malignancy of any type, or has been diagnosed with cancer within the past 5 years. Basal cell carcinoma of the skin that has been successfully treated will be permitted. * Known or suspected history of Human Immunodeficiency Virus. * Positive Hepatitis Screen * Clinically significant abnormalities in clinical chemistry, hematology or urinalysis * Received any investigational drug within 1 month of study * History of major psychiatric disorder * Active or uncontrolled seizure disorder. * Requires treatment with monoamine oxidase inhibitors (MAOIs), or tricyclic antidepressants during the course of the study. * Surgical procedure planned, or scheduled during the course of this study. * Ongoing workman's compensation claim or litigation. * Previous participation in the M03-666 study.