The purpose of this study is to evaluate the analgesic efficacy and safety of oxymorphone extended release in opioid-experienced patients with chronic low back pain.

Patients with chronic low back pain on stable opioid treatment will be converted to oxymorphone extended release (ER)and enter an open-label treatment phase.During the Open-Label Titration Period (up to 28 days), patients will receive daily oxymorphone ER PO q12h. Patients stabilized on a dose that provides adequate pain relief will be randomized to either continue on the stabilized dose of oxymorphone ER or receive placebo in a double-blind fashion for a total duration of 12 weeks.

Inclusion Criteria:

• Males or females 18 years of age or older
• In good health as determined by the Investigator on the basis of medical history and physical examination.
• Moderate to severe chronic non-neuropathic low back pain that has been present daily for at least several hours per day for a minimum of three months prior to the screening.
• On a stable around-the-clock opioid pain medication for the management of moderate to severe chronic lower back pain.
• Expected to require a total daily oxymorphone ER dose that is a minimum of 20 mg per day (oral morphine equivalent: approximately 60 mg) and will not exceed 220 mg oxymorphone ER (oral morphine requirement: approximately 660 mg).
• Any adjunct therapy for back pain such as physical therapy, biofeedback therapy, acupuncture therapy or herbal remedies, based on the patient's current status should remain unchanged during the period of participation of the patient.
• Written informed consent

Exclusion Criteria:

• Pregnant and/or lactating
• Subjects with radiculopathy, fibromyalgia, reflex sympathetic dystrophy or causalgia (complex regional pain syndrome), acute spinal cord compression, cauda equina compression, acute nerve root compression, severe lower extremity weakness or numbness, bowel or bladder dysfunction secondary to cauda equina compression, diabetic amyotrophy, meningitis, discitis, or back pain due to secondary infection or tumor.
• Cannot or will not agree to stop local regional pain treatments during the study (nerve/plexus blocks or ablation, neurosurgical procedures for pain control, Botulinum toxin injections, or inhalation analgesia). The patient must not have a nerve/plexus block within 4 weeks of screening (Visit 1). The patient must not have a Botulinum toxin injection in the lower back region within 3 months of screening.
• Intend to alter their physical therapy regimen during the study.
• Surgical procedures directed towards the source of back pain within 6 months of screening.
• Pain which is secondary to confirmed or suspected neoplasm.
• Dysphagia or difficulty swallowing tablets or capsules.
• Significant prior history of substance abuse or alcohol abuse.
• Use of any investigational medication within 30 days prior to the first dose of study medication.
• Previous exposure to oxymorphone.
• History of clinically significant intolerance to oxymorphone or a known hypersensitivity to opioid analgesics.
• History of seizure.
• use of MAO inhibitor within 14 days prior to the start of study medication.
• Other clinically significant conditions as judged by the investigator.