Breakthrough PainAdministration, BuccalFentanylLabor PainAnalgesics, OpioidPainAnalgesia, EpiduralPain MeasurementDouble-Blind MethodNeoplasmsChronic DiseaseChronic PainPain ManagementPain ThresholdPain, PostoperativeRadionuclide GeneratorsPain, IntractableLow Back PainBack PainAbdominal PainNeck PainPelvic PainPain PerceptionFacial Pain