CarbolinesPhosphodiesterase 5 InhibitorsPhosphodiesterase InhibitorsErectile DysfunctionCyclic Nucleotide Phosphodiesterases, Type 5SulfonesTriazinesPurinesImpotence, VasculogenicUrological AgentsPenile Erection3',5'-Cyclic-GMP PhosphodiesterasesPiperazinesPoisonsTribulusFlushingImidazolesCell-Derived MicroparticlesPenisPhosphoric Diester HydrolasesLower Urinary Tract SymptomsHypertension, PulmonaryCyclic GMPCyclic GMP-Dependent Protein KinasesUrologic DiseasesNociceptionVasodilator AgentsDouble-Blind MethodCross-Over StudiesProstatic HyperplasiaUrinary TractOxadiazolesNiacinCystathionine beta-SynthasePhenylpropionatesHydrogen SulfideTreatment OutcomeSurvivalOncogene Protein v-aktPlacebosExercise ToleranceSulfonamidesNitroglycerinQuinoxalinesHypotensionPatient SatisfactionCardiotonic AgentsGuanylate CyclaseDrug Administration ScheduleCardiomyopathiesCarnitineItaly