MethadoneNarcoticsOpiate Substitution TreatmentInjectionsOpioid-Related DisordersHeroin DependenceMethadyl AcetateBrain ChemistryAnalgesics, OpioidBuprenorphineBrain InjuriesNeonatal Abstinence SyndromeHeroinBrain NeoplasmsBrain MappingInjections, IntravenousBrainInjections, IntramuscularSubstance Abuse DetectionSubstance Abuse, IntravenousInjections, SubcutaneousPyrrolidinesDrug OverdoseInjections, IntralesionalMorphineBrain EdemaBrain StemDose-Response Relationship, DrugTime FactorsInjections, Intra-ArticularInjections, IntraperitonealNarcotic AntagonistsBrain IschemiaRats, Sprague-DawleySubstance Withdrawal SyndromeStreet DrugsSubstance-Related DisordersMagnetic Resonance ImagingDextropropoxypheneCocaine-Related DisordersNaloxoneOpiumDisease Models, AnimalBrain AbscessNeuronsInjections, IntraventricularDrug InteractionsInjections, SpinalStereoisomerismPainInjections, IntradermalOxidoreductases, N-DemethylatingInjections, EpiduralCocaineInjections, Intra-ArterialMeconiumTissue DistributionBlood-Brain BarrierCerebral CortexMice, Inbred C57BLTherapeutic CommunityTreatment OutcomeNaltrexonePrisonersRats, WistarIntravitreal InjectionsHypoxia, BrainDirectly Observed TherapyHarm ReductionPregnancyReceptors, Opioid, muBehavior, AnimalAnalysis of VarianceInjections, JetCodeinePupilInjections, IntraocularCytochrome P-450 CYP3A