SulfonesPurinesPhosphodiesterase 5 InhibitorsPiperazinesPhosphodiesterase InhibitorsCyclic Nucleotide Phosphodiesterases, Type 5Erectile Dysfunction3',5'-Cyclic-GMP PhosphodiesterasesVasodilator AgentsPenile ErectionHypertension, PulmonaryCarbolinesImpotence, VasculogenicCyclic GMPPenisPhosphoric Diester HydrolasesPyrimidinonesAdministration, OralTriazinesPulmonary ArteryPriapismCross-Over StudiesDouble-Blind MethodNitric OxideClitorisCyclic GMP-Dependent Protein KinasesHypertrophy, Right VentricularPulmonary Wedge PressureVascular ResistanceDihydroergocristineTreatment OutcomeDose-Response Relationship, DrugIloprostPapaverineHemodynamicsEjaculationDrug Therapy, CombinationBlood PressureAntihypertensive AgentsAlprostadilEpimediumCyclic Nucleotide Phosphodiesterases, Type 2Drug InteractionsGuanylate CyclasePentylenetetrazoleCoitusPulmonary CirculationEsophageal Motility DisordersOrgasmVasodilationCREST SyndromeDrug SynergismMilrinoneMonocrotalineEpoprostenolRats, WistarMagnesium HydroxideNG-Nitroarginine Methyl EsterTime FactorsDisease Models, AnimalImidazolesSulfonamidesPurinonesCardiomyopathy, RestrictiveCyclic GMP-Dependent Protein Kinase Type IDoxazosinHeart RateExercise ToleranceExercise TestPentaerythritol TetranitratePlacebosSteroid 16-alpha-HydroxylaseMice, Inbred ICRRegional Blood FlowNitric Oxide DonorsPhentolamineCyclic Nucleotide Phosphodiesterases, Type 3VasovasostomyIsosorbide DinitrateArterial PressureOxadiazolesMidodrineNitric Oxide Synthase Type IIIPatient SatisfactionPersistent Fetal Circulation SyndromeLibidoNitric Oxide SynthaseMagnesium CompoundsSafetyScleroderma, LimitedNitroglycerinRats, Sprague-DawleyBufonidaeAnoxiaRhinomanometryOcular HypotensionPlacental CirculationCecal DiseasesMethylene BlueHeadache