A Pilot Study of Switching From One Pain Medication to Another (Opioid Rotation)

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)