AnalgesicsAnalgesics, OpioidPharmacologyPharmacology, ClinicalAnalgesics, Non-NarcoticAnalgesiaPainPain MeasurementMorphinePain, PostoperativeTramadolPhenacetinAcetaminophenDextropropoxypheneDrug ToleranceAnti-Inflammatory Agents, Non-SteroidalDose-Response Relationship, DrugCodeinePain ThresholdReceptors, Opioid, muFentanylInjections, SpinalAnesthetics, LocalHyperalgesiaMeperidinePentazocinePain ManagementOxycodoneDipyroneReceptors, OpioidDouble-Blind MethodNaloxoneBupivacaineAnalgesia, EpiduralNarcotic AntagonistsAnalgesia, Patient-ControlledRats, Sprague-DawleyCarrageenanKetoprofenHypnotics and SedativesKidney Papillary NecrosisTolmetinNefopamHydrocodoneKetorolacPain, IntractableIbuprofenNociceptionNeuralgiaPortographyNalorphineEdemaAcupuncture AnalgesiaCyclohexanecarboxylic AcidsBuprenorphineNarcoticsPharmaceutical PreparationsNociceptorsDrug DiscoveryDrug Evaluation, PreclinicalDiclofenacAnalgesia, ObstetricalDrug InteractionsButorphanolOxymorphoneRadioligand AssayTime FactorsAdministration, OralSinomeniumMorphine DerivativesReceptors, G-Protein-CoupledLigandsPiperidinesMorphinansAmidesMeptazinolBehavior, AnimalReceptors, Opioid, deltaInternational AgenciesPharmacokineticsNociceptive PainClonidineAnti-Inflammatory AgentsDrug DesignCannabinoidsAlfentanilAntipyreticsKetamineAcetic AcidOpioid PeptidesNalbuphineInjections, IntravenousAcute PainNerve BlockPlant ExtractsTerminology as TopicChronic PainNitrous OxideDexmedetomidineAmines