title: Demand analgesia to assess pain relief from epidural opiates.
mesh_terms: D000763:Anesthesia, Caudal / Q000379:methods*; D000767:Anesthesia, Epidural / Q000379:methods*; D001416:Back Pain / Q000188:drug therapy*; D003201:Computers; D005283:Fentanyl / Q000008:administration & dosage*; D003932:Heroin / Q000627:therapeutic use*; D006801:Humans; D007275:Injections, Intravenous; D012646:Self Administration / Q000379:methods
chemical_list: D003932:Heroin; D005283:Fentanyl