Clinical trials of analgesic drugs.
D000700:Analgesics / Q000627:therapeutic use*; D001062:Appendectomy; D002763:Cholecystectomy; D002986:Clinical Trials as Topic; D006801:Humans; D008691:Methadone / Q000627:therapeutic use; D010880:Piperidines / Q000627:therapeutic use; D010919:Placebos; D012106:Research
D000700:Analgesics; D010880:Piperidines; D010919:Placebos; D008691:Methadone