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

- 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

- 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.