Administration, OralDrug Administration ScheduleInjections, IntravenousUnited States Food and Drug AdministrationDrug Administration RoutesDose-Response Relationship, DrugRats, Sprague-DawleyTime FactorsAdministration, IntranasalRats, WistarInjections, IntraperitonealDisease Models, AnimalInjections, SubcutaneousAdministration, RectalLiverMice, Inbred C57BLBiological AvailabilityInjections, IntramuscularAdministration, TopicalInfusions, IntravenousHalf-LifeAdministration, IntravenousDrug InteractionsArea Under CurveInjections, IntraventricularMice, Inbred BALB CRats, Inbred StrainsAdministration, CutaneousTissue DistributionDogsDouble-Blind MethodCross-Over StudiesTreatment OutcomeBlood PressureAdministration, SublingualBrainAdministration, InhalationKidneyInfusions, ParenteralBody WeightRandom AllocationBehavior, AnimalDrug ToleranceMorphineRecombinant ProteinsPlant ExtractsInjectionsAnalysis of VarianceInjections, SpinalOrgan SizeMetabolic Clearance RateChromatography, High Pressure LiquidRNA, MessengerRabbitsMice, Inbred ICRLungRats, Inbred F344Analgesics, OpioidSelf AdministrationEthanolHeart RatePregnancyEstradiolMotor ActivityAntineoplastic AgentsDrug CombinationsMice, KnockoutHemodynamicsMice, Inbred StrainsDrug Evaluation, PreclinicalAnalgesicsDrug Therapy, CombinationEnzyme InhibitorsInjections, Intra-ArterialAdministration, BuccalSpleenPiperidinesProdrugsAntibodies, MonoclonalIntestinal AbsorptionBlood GlucoseDrug ApprovalAnti-Inflammatory Agents, Non-SteroidalDrug SynergismCocaineNaloxoneEatingUnited StatesDopamineGenetic TherapyNitric OxideCytokinesHydrocortisoneAbsorptionCells, CulturedLipopolysaccharidesImmunohistochemistryDelayed-Action PreparationsInsulinPain Measurement