Administration, CutaneousFentanylAnalgesics, OpioidPainTransdermal PatchPain, IntractableMorphineDosage FormsReceptors, Opioid, muOxycodoneReceptors, OpioidSkin AbsorptionReceptors, Opioid, deltaDelayed-Action PreparationsPain MeasurementCancer Care FacilitiesReceptors, Opioid, kappaPalliative CarePain, PostoperativeAdministration, OralNeoplasmsOpioid PeptidesChronic DiseaseNarcotic AntagonistsNaloxoneNarcoticsNaltrexoneOpioid-Related DisordersDouble-Blind MethodAnesthetics, IntravenousBuprenorphineDrug Delivery SystemsDrug ToleranceAnalgesia, EpiduralEnkephalin, Ala(2)-MePhe(4)-Gly(5)-IontophoresisSkinSufentanilAlfentanilPhonophoresisEnkephalinsPharmaceutical VehiclesNeedlesNitroglycerinAnalgesicsAnalgesiaAdjuvants, AnesthesiaChemistry, PharmaceuticalAnalgesia, Patient-ControlledBupivacaineEnkephalin, D-Penicillamine (2,5)-Anesthesia, IntravenousEndorphinsEstrogen Replacement TherapyDose-Response Relationship, DrugHydromorphonePreanesthetic MedicationAnalgesia, ObstetricalAnesthetics, CombinedNicotineEnkephalin, LeucineAnesthesia, GeneralRats, HairlessPropofolAnesthetics, LocalInjections, SpinalDynorphinsDrug InteractionsSkin Irritancy Testsbeta-EndorphinEnkephalin, Leucine-2-AlanineMidazolamPermeabilityAnesthesia Recovery PeriodDiffusion Chambers, CultureBenzeneacetamidesDrug Administration ScheduleTime FactorsDrug CarriersSubstance Withdrawal SyndromeNitrous OxideInfusions, IntravenousInjections, IntravenousMethadoneScopolamine HydrobromideDydrogesteroneMorphinansMeperidineDiprenorphineRats, Sprague-DawleyBreakthrough PainTechnology, PharmaceuticalDrug CompoundingTreatment OutcomeCross-Over StudiesEmulsionsMyristatesBiological AvailabilityGelsAnesthetics, Inhalation