AnalgesicsAnalgesics, OpioidReceptors, Opioid, muReceptors, OpioidReceptors, Opioid, deltaReceptors, Opioid, kappaPainOpioid PeptidesAnalgesics, Non-NarcoticTreatment OutcomeMorphineNarcotic AntagonistsClinical Trials as TopicTissue EngineeringWound HealingAnalgesiaDisease Models, AnimalNaloxonePain MeasurementCell Line, TumorDrug Resistance, NeoplasmPrognosisTime FactorsOpioid-Related DisordersAntineoplastic AgentsCell ProliferationNaltrexoneAnti-Bacterial AgentsPredictive Value of TestsBiological MarkersPain, PostoperativeEnkephalinsNarcoticsTramadolEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Drug ToleranceBuprenorphineRisk FactorsEndorphinsFentanylEnkephalin, D-Penicillamine (2,5)-DynorphinsPhenacetinAcetaminophenHydromorphonePain ThresholdEnkephalin, LeucineMorphinansDextropropoxypheneCodeineInjections, SpinalDose-Response Relationship, DrugEnkephalin, Leucine-2-AlanineAnti-Inflammatory Agents, Non-SteroidalHyperalgesiabeta-EndorphinPain ManagementMeperidineMethadonePentazocineBenzeneacetamidesPain, IntractableDiprenorphineAnesthetics, LocalChronic PainButorphanolDouble-Blind MethodHydrocodoneOxymorphoneRats, Sprague-DawleyMorphine DerivativesDipyroneAnalgesia, EpiduralLevorphanolAnalgesia, Patient-ControlledBenzomorphansBupivacaineOxycodoneSubstance Withdrawal SyndromeNociceptorsNociceptionAlfentanilCyclazocinePrescription DrugsNalbuphinePyrrolidinesCarrageenanHeroinNeuralgiaTolmetinKetoprofenSufentanilMeptazinolKetorolacAcupuncture AnalgesiaMorphine DependenceNalorphineBehavior, AnimalDrug OverdoseKidney Papillary Necrosis