CarbolinesSulfonesPurinesPhosphodiesterase 5 InhibitorsPiperazinesPhosphodiesterase InhibitorsCyclic Nucleotide Phosphodiesterases, Type 5Erectile Dysfunction3',5'-Cyclic-GMP PhosphodiesterasesVasodilator AgentsPenile ErectionHypertension, PulmonaryMAP Kinase Kinase KinasesImpotence, VasculogenicCyclic GMPPenisPhosphoric Diester HydrolasesPyrimidinonesAdministration, OralTriazinesPulmonary ArteryAdaptor Proteins, Signal TransducingPriapismCross-Over StudiesDouble-Blind MethodNitric OxideClitorisCyclic GMP-Dependent Protein KinasesTNF Receptor-Associated Factor 6Hypertrophy, Right VentricularPulmonary Wedge PressureVascular ResistanceDihydroergocristineTreatment OutcomeMitogen-Activated Protein Kinase 14Dose-Response Relationship, DrugIloprostPapaverineHemodynamicsEjaculationDrug Therapy, Combination