- Participants who have fibromyalgia (neurosensory disorder characterized by muscle pain, joint stiffness, and fatigue), reflex sympathetic dystrophy (feeling of pain associated with evidence of minor nerve injury) or causalgia (persistent, severe burning sensation of the skin), acute spinal cord compression, acute nerve root compression, severe lower extremity weakness or numbness, regional pain syndrome, meningitis (inflammation of the meninges), diskitis (nonbacterial inflammation of an intervertebral disk or disk space), back pain because of secondary infection or tumor, or pain caused by a confirmed or suspected neoplasm