Opioid-Related DisordersBuprenorphineNarcotic AntagonistsOpiate Substitution TreatmentAnalgesics, OpioidMethadoneNaloxoneNarcoticsReceptors, Opioid, muReceptors, OpioidNaltrexoneSubstance Withdrawal SyndromeHeroin DependenceMethadyl AcetateReceptors, Opioid, deltaReceptors, Opioid, kappaOpiate AlkaloidsMorphine DependenceHeroinOpioid PeptidesSheltered WorkshopsCocaine-Related DisordersMorphineSubstance Abuse DetectionPrescription Drug MisuseHydromorphoneDiprenorphineNeonatal Abstinence SyndromePrescription DrugsSubstance Abuse Treatment CentersUrine Specimen CollectionDrug ToleranceSubstance-Related DisordersBehavior, AddictivePainDrug InteractionsAlcoholismTreatment OutcomeDose-Response Relationship, DrugEnkephalinsMedication AdherenceDiagnostic and Statistical Manual of Mental DisordersEnkephalin, Ala(2)-MePhe(4)-Gly(5)-CounselingSubstance Abuse, IntravenousBehavior TherapyDouble-Blind MethodTime FactorsEnkephalin, D-Penicillamine (2,5)-DynorphinsEndorphinsDrug CombinationsDrug Administration ScheduleCocainePrimary Health CareChronic DiseaseEnkephalin, LeucineHIV InfectionsEnkephalin, Leucine-2-AlanineUnited StatesCombined Modality TherapyTobacco Use Disorderbeta-EndorphinAnalgesicsBenzeneacetamidesSeverity of Illness IndexMorphinansFentanylCase-Control StudiesPain MeasurementKineticsBenzomorphansPyrrolidinesAnalgesiaRats, Sprague-DawleyLevorphanolChronic PainHydrogen-Ion ConcentrationTemperatureButorphanolMarijuana AbuseOligopeptidesDiterpenes, ClerodaneMorphine DerivativesMembrane PotentialsOxymorphone