• Patient Global Impression of Change [ Time Frame: end of study ] [ Designated as safety issue: No ]
• Brief Pain Inventory [ Time Frame: ssessed daily for 10 days prior to IV PCA treatment, and assessed daily for 2 weeks after IV PCA treatment ] [ Designated as safety issue: No ]

he purpose of this study is to see if changing from one pain medication like morphine or oxycodone to another pain medication, oxymorphone (OPANA®), will be helpful to patients. This study will examine if the swithcing from one pain medication to another can be done over a 24 hour period. Oxymorhone, the drug being studied, is an FDA approved drug for treatment of severe pain.

Inclusion Criteria:

• Age of 18 to no upper limit
• Chronic pain of nociceptive, neuropathic, or mixed origin
• Patients with chronic non cancer pain
• Ongoing chronic opioid treatment with either oral morphine or oxycodone (long term - more than 3 months of at least a total daily opioid dose of 60 mg morphine or of 30 mg oxycodone)
• Pain of moderate intensity (>4, on the numerical scale 0-10) despite ongoing opioid therapy>
• Non-pregnant, non-lactating women
• Sufficient language skills to communicate with research staff

Exclusion Criteria:Non-ambulatory patients

• Clinically significant respiratory, renal, hepatic, or cardiac disease.
• Documented diagnosis of sleep apnea (the study physician may exclude patients who present with clinical features and complaints suggestive of a diagnosis of probable sleep apnea)
• History of illicit drug or alcohol dependence or abuse, abnormal drug taking / seeking behaviors
• Severe depression (> 26 on the BDI)
• Patients who exhibit a score on the Mini Mental Status Exam (MMSE) of 26 or less. (The range of scores for mild dementia is 21-26 on the MMSE).
• Workman compensation, current or pending medical-legal litigation
• Hypersensitivity to study medication (oxymorphone)