6-MercaptopurineThioguanineAzathioprineChromatography, High Pressure LiquidImmunosuppressive AgentsCalibrationMethyltransferasesMethylthioinosineNucleotidesLimit of DetectionGuanine NucleotidesReproducibility of ResultsHypoxanthine PhosphoribosyltransferaseSpectrophotometry, UltravioletAzaguanineInflammatory Bowel DiseasesReference StandardsAntimetabolitesAntimetabolites, AntineoplasticThionucleotidesPrecursor Cell Lymphoblastic Leukemia-LymphomaThionucleosidesAcetonitrilesChromatography, Reverse-PhaseFlow Injection AnalysisHypoxanthinesSolid Phase ExtractionSensitivity and SpecificityPurine NucleotidesPurinesMethotrexateChromatography, LiquidDrug StabilityTandem Mass SpectrometryPrednisoloneTabletsCytarabineCrohn DiseaseSpectrometry, Mass, Electrospray IonizationGas Chromatography-Mass SpectrometryDaunorubicinAzauridineVeterinary DrugsChromatography, GasDrug ContaminationIndicators and ReagentsMolecular Sequence DataAminosalicylic AcidsPrednisoneElectrophoresis, CapillaryChemistry Techniques, AnalyticalMesalamineTime FactorsDrugs, Chinese HerbalChromatography, Micellar Electrokinetic CapillaryColitis, UlcerativePharmaceutical PreparationsRemission InductionElectrochemistryGuanineAdenine NucleotidesDrug ResistanceKineticsPotassium CompoundsAdministration, OralLiquid-Liquid ExtractionErythrocytesRutinGastrointestinal AgentsQuality ControlDrug Therapy, CombinationLeast-Squares AnalysisProdrugsSilica GelElectrodesLaboratory Proficiency TestingAsparaginaseEthylaminesMicrochemistryMethanolMycophenolic AcidChlorogenic AcidInosine MonophosphateThioinosineDosage FormsTrifluoroacetic AcidSpectrophotometryDNAPolymorphism, Single NucleotideCapillary ActionDose-Response Relationship, Drug3,4-MethylenedioxyamphetamineAmino Acid SequenceBiotransformationPhosphoribosyl PyrophosphateHydrogen-Ion ConcentrationSulfasalazineKidney TransplantationHypoxanthineCyclosporine