MorphineAnalgesiaAnalgesia, EpiduralAnalgesia, ObstetricalAnalgesics, OpioidAnalgesia, Patient-ControlledMorphine DerivativesMorphine DependencePain, PostoperativePain MeasurementDrug ToleranceNaloxoneAnalgesicsBupivacaineFentanylNarcoticsAnesthetics, LocalInjections, SpinalReceptors, Opioid, muPainAcupuncture AnalgesiaMeperidineNarcotic AntagonistsAnesthesia, EpiduralSufentanilLabor PainCodeineNerve BlockReceptors, OpioidHydromorphoneAnesthesia, ObstetricalTramadolDouble-Blind MethodPain ThresholdAnesthesia, SpinalLabor, ObstetricAnalgesics, Non-NarcoticSubstance Withdrawal SyndromeAmidesNalbuphineDose-Response Relationship, DrugPostoperative Nausea and VomitingPeriaqueductal GrayNaltrexonePentazocineOxycodoneKetorolacHeroinCesarean SectionClonidineRats, Sprague-DawleyEnkephalin, Ala(2)-MePhe(4)-Gly(5)-KetamineEnkephalinsMorphinansAnesthesia, GeneralReceptors, Opioid, deltaPruritusHyperalgesiaLidocaineOpioid PeptidesInterpleural AnalgesiaButorphanolConscious SedationPain ManagementPirinitramideAlfentanilPain, IntractableSpinal CordOpiumLabor Stage, FirstNalorphineAnesthesia, CaudalBehavior, AnimalOxymorphoneReceptors, Opioid, kappaHypnotics and SedativesEndorphinsInjections, IntravenousPregnancyFemoral NerveNociceptorsThoracotomyAnesthesia and AnalgesiaBuprenorphineHysterectomyDrug Administration ScheduleDipyronePostoperative CareDrug InteractionsInjections, SubcutaneousInjections, IntraventricularElectroacupunctureAnesthetics, CombinedPiperidinesProspective StudiesTime FactorsKetoprofenAnesthesia, ConductionAdjuvants, Anesthesia