title: Letter: Potencies of fentanyl and morphine.
mesh_terms: D004329:Droperidol; D004357:Drug Synergism; D005069:Evaluation Studies as Topic; D005283:Fentanyl; D006801:Humans; D009020:Morphine; D009458:Neuroleptanalgesia; D011229:Preanesthetic Medication; D012119:Respiration / Q000187:drug effects
chemical_list: D009020:Morphine; D004329:Droperidol; D005283:Fentanyl