Drug ToleranceBenzyl AlcoholMorphineDrug Resistance, FungalPainPain MeasurementAnalgesics, OpioidMorphine DependencePain, PostoperativeMorphine DerivativesPain ManagementAnalgesicsChronic PainImmune TolerancePain, IntractableBack PainAnalgesiaPain ThresholdOxycodoneReceptors, Opioid, muFacial PainNarcoticsNaloxoneTramadolBrachial Plexus NeuritisGlucose Tolerance TestLow Back PainNeuralgiaAbdominal PainFentanylNeck PainAnalgesia, Patient-ControlledAnesthetics, LocalPain PerceptionNarcotic AntagonistsInjections, SpinalTransplantation TolerancePelvic PainTreatment OutcomeHyperalgesiaChronic DiseaseAcute PainDouble-Blind MethodLidocaineAnalgesics, Non-NarcoticTime FactorsDose-Response Relationship, DrugPain, ReferredSubstance Withdrawal SyndromeProspective Studies