Receptors, Opioid, muAnalgesics, OpioidReceptors, OpioidReceptors, Opioid, deltaReceptors, Opioid, kappaOpioid PeptidesNarcotic AntagonistsNaltrexoneNaloxoneOpioid-Related DisordersMorphineEnkephalin, Ala(2)-MePhe(4)-Gly(5)-EnkephalinsNarcoticsEnkephalin, D-Penicillamine (2,5)-EndorphinsHydromorphoneDynorphinsBuprenorphinePainEnkephalin, LeucineHeroin DependenceEnkephalin, Leucine-2-AlanineFentanylDiprenorphineHydrocodoneObstetric Surgical Proceduresbeta-EndorphinAnalgesiaPain MeasurementBenzeneacetamidesAnalgesicsBacterial Outer Membrane ProteinsPseudomonas aeruginosaDrug ToleranceMorphinansMethadoneMembrane Transport ProteinsMorphine DerivativesBenzomorphansPolymorphism, Single NucleotidePyrrolidinesSubstance Withdrawal SyndromeOpiate Substitution TreatmentAlcoholismDrug Resistance, MultipleHeroinChronic PainGenotypePrescription Drug MisuseLevorphanolDose-Response Relationship, DrugMorphine DependenceButorphanolPrescription DrugsPain, PostoperativeDiterpenes, ClerodaneReceptors, Dopamine D4OxymorphonePeriplasmEthylketocyclazocinePharmacogeneticsInjections, SpinalRejection (Psychology)Rats, Sprague-DawleyPain, IntractableOligopeptidesBenzylidene CompoundsTriclosanDrug OverdosePain ThresholdCyclazocineCatechol O-MethyltransferaseAnalgesics, Non-NarcoticSubstance-Related DisordersGenetic Association StudiesAnalgesia, Patient-ControlledObject AttachmentPeriaqueductal GrayD-Ala(2),MePhe(4),Met(0)-ol-enkephalinHeredityHyperalgesiaAlfentanilNalbuphineArrestinsTramadolGuanosine 5'-O-(3-Thiotriphosphate)Polymorphism, GeneticBrainMolecular Sequence DataDrug InteractionsRadioligand AssaySufentanilGynecologic Surgical ProceduresLoperamideAllelesOpiate AlkaloidsPain ManagementDrug Resistance, MicrobialMethadyl Acetate