Administration, OralDrug Administration RoutesInjections, IntravenousDrug Administration ScheduleUnited States Food and Drug AdministrationDose-Response Relationship, DrugRats, Sprague-DawleyTime FactorsAdministration, IntranasalInjections, IntraperitonealRats, WistarInjections, SubcutaneousDisease Models, AnimalAdministration, RectalInjections, IntramuscularMice, Inbred C57BLBiological AvailabilityLiverHalf-LifeAdministration, TopicalInfusions, IntravenousAdministration, IntravenousArea Under CurveInjections, IntraventricularMice, Inbred BALB CDrug InteractionsAdministration, CutaneousTissue DistributionRats, Inbred StrainsDogsAdministration, SublingualDouble-Blind MethodTreatment OutcomeCross-Over StudiesAdministration, InhalationBrainBlood PressureKidneyRandom AllocationBody WeightInjectionsInfusions, ParenteralBehavior, AnimalRecombinant ProteinsMorphineDrug ToleranceChromatography, High Pressure LiquidInjections, SpinalPlant ExtractsAnalysis of VarianceMetabolic Clearance RateLungMice, Inbred ICROrgan SizeRNA, MessengerRats, Inbred F344RabbitsAnalgesics, OpioidPregnancyEthanolSpleenSelf AdministrationAntineoplastic AgentsMice, Inbred StrainsHeart RateEstradiolMotor ActivityInjections, Intra-ArterialDrug CombinationsDrug Evaluation, PreclinicalAnalgesicsHemodynamicsEnzyme InhibitorsMice, KnockoutIntestinal AbsorptionDrug Therapy, CombinationProdrugsPiperidinesAntibodies, MonoclonalAnti-Inflammatory Agents, Non-SteroidalAdministration, BuccalBlood GlucoseAbsorptionCells, CulturedBiotransformationDrug ApprovalDrug SynergismCocaineUnited StatesInjections, IntradermalEatingNaloxoneKineticsGenetic TherapyCytokinesDrug Delivery SystemsImmunohistochemistryAdministration, IntravaginalGenetic VectorsNitric Oxide