MeperidineAnalgesics, OpioidReceptors, Opioid, muReceptors, OpioidReceptors, Opioid, deltaReceptors, Opioid, kappaShiveringOpioid PeptidesAdjuvants, AnesthesiaAnalgesia, ObstetricalNaloxoneMorphineNarcotic AntagonistsPromethazineNarcoticsHydroxyzineFentanylDihydroergotamineOpioid-Related DisordersAlfentanilNaltrexoneAnalgesia, EpiduralButorphanolPain MeasurementEnkephalinsConscious SedationPreanesthetic MedicationAnalgesia, Patient-ControlledEnkephalin, Ala(2)-MePhe(4)-Gly(5)-SufentanilCesarean SectionAnalgesics, Non-NarcoticChloral HydrateDextropropoxypheneAnalgesicsEnkephalin, D-Penicillamine (2,5)-PainEndorphinsKetorolac TromethamineInjections, SpinalDynorphinsKetorolacAnesthesia, SpinalBuprenorphinePain, PostoperativeAnesthetics, LocalTolmetinAnalgesiaSkin TemperatureEnkephalin, LeucineSerotonin SyndromeAnesthesia, DentalAnesthesia, EpiduralEnkephalin, Leucine-2-AlanineTramadol