title: Spinal opioids: historical perspectives and future directions. Introduction.
authors.forename: S D
authors.initials: SD
authors.lastname: Waldman
authors.forename: T L
authors.initials: TL
authors.lastname: Yaksh
mesh_terms: D015360:Analgesia, Epidural / Q000639:trends*; D005544:Forecasting; D006801:Humans; D009294:Narcotics / Q000008:administration & dosage* / Q000627:therapeutic use; D010146:Pain / Q000188:drug therapy*
chemical_list: D009294:Narcotics