Analgesics, OpioidPainAnalgesicsPain MeasurementPain ManagementReceptors, Opioid, muChronic PainReceptors, OpioidPain, PostoperativeReceptors, Opioid, deltaPrescription Drug MisusePain, IntractableReceptors, Opioid, kappaOpioid PeptidesArthralgiaMedication ErrorsMedication AdherenceNeuralgiaPalliative CareTreatment OutcomePain ThresholdNarcotic AntagonistsQuestionnairesAnti-Inflammatory Agents, Non-SteroidalProspective StudiesOpioid-Related DisordersLow Back PainBack PainNaloxoneSeverity of Illness IndexQuality of LifePatient SatisfactionNaltrexoneRetrospective StudiesAbdominal PainNeck PainTime FactorsComorbidityMedication ReconciliationMedication SystemsMorphineFollow-Up StudiesMedication Systems, HospitalCohort StudiesPain PerceptionPelvic PainAcute PainNarcoticsEnkephalinsFacial PainEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Prescription DrugsBuprenorphinePain, ReferredEnkephalin, D-Penicillamine (2,5)-EndorphinsDynorphinsDrug PrescriptionsShoulder PainMusculoskeletal PainSelf MedicationEnkephalin, LeucineAnalgesiaChronic DiseasePatient ComplianceEnkephalin, Leucine-2-AlaninePolypharmacyFentanylMethadonePsychotropic DrugsDrug Therapybeta-EndorphinDiprenorphineNociceptive PainHyperalgesiaDrug ToleranceHydromorphoneDrug UtilizationDouble-Blind MethodBenzeneacetamidesUnited StatesMorphinansSubstance Withdrawal SyndromeNonprescription DrugsAntipsychotic AgentsDose-Response Relationship, DrugAnalgesics, Non-NarcoticOpiate Substitution TreatmentDrug-Related Side Effects and Adverse Reactions