OxycodoneAnalgesics, OpioidOxymorphoneAnalgesicsReceptors, Opioid, muOpioid-Related DisordersReceptors, OpioidHydrocodonePainMorphineReceptors, Opioid, deltaTramadolReceptors, Opioid, kappaMorphinansNarcotic AntagonistsAnalgesics, Non-NarcoticPain MeasurementMeptazinolNarcoticsNaloxoneFentanylAnalgesiaChronic PainCodeineMeperidineDrug ToleranceOpioid PeptidesHydromorphoneDextropropoxypheneDrug and Narcotic ControlAcute PainPain, PostoperativeMorphine DerivativesPrescription Drug MisusePrescription DrugsButorphanolNaltrexoneBuprenorphinePain ManagementPentazocineDrug PrescriptionsPain, IntractableAcetaminophenMethadoneEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Pain ThresholdDelayed-Action PreparationsDose-Response Relationship, DrugDouble-Blind MethodNalbuphineForensic MedicineAlfentanilInappropriate PrescribingDrug InteractionsInjections, SpinalOpiate AlkaloidsUncompensated CareMiosisEnkephalinsAnti-Inflammatory Agents, Non-SteroidalSubstance Abuse DetectionCyclohexanecarboxylic AcidsPharmaceutical ServicesEndorphinsPoisoningEnkephalin, D-Penicillamine (2,5)-Rats, Sprague-DawleyBenzomorphansSubstance-Related DisordersCytochrome P-450 CYP2D6Drug OverdoseDynorphinsPhenacetinChronic Disease