Naloxone and placebo.
D000698:Analgesia; D006801:Humans; D009270:Naloxone / Q000627:therapeutic use*; D009619:Nociceptors / Q000187:drug effects; D010146:Pain / Q000188:drug therapy*; D010919:Placebos
D010919:Placebos; D009270:Naloxone