Breakthrough PainAdministration, BuccalAnalgesics, OpioidFentanylPainAnalgesicsLabor PainAnalgesia, EpiduralAnalgesia, ObstetricalPain MeasurementBupivacaineMorphineDouble-Blind MethodNasal SpraysNaloxonePain, PostoperativeNeoplasmsChronic DiseaseAnalgesics, Non-NarcoticPain ManagementPain ThresholdChronic PainAnalgesiaPain, IntractableLow Back PainRadionuclide GeneratorsBack PainAnesthetics, LocalTreatment OutcomeAnesthetics, IntravenousAbdominal PainTramadolNeck PainTime FactorsPain PerceptionAnalgesia, Patient-ControlledSufentanilAcute PainAlfentanilFacial PainAdministration, CutaneousInjections, SpinalReceptors, Opioid, muPelvic PainAdjuvants, AnesthesiaEpisode of CareAerosolsAnesthesia, IntravenousPreanesthetic MedicationMeperidineDose-Response Relationship, DrugDrug ToleranceProspective Studies