SulfonesPurinesPiperazinesPhosphodiesterase 5 InhibitorsPhosphodiesterase InhibitorsErectile DysfunctionCyclic Nucleotide Phosphodiesterases, Type 53',5'-Cyclic-GMP PhosphodiesterasesPenile ErectionVasodilator AgentsCitrate (si)-SynthaseClitorisCyclic GMPBufonidaeOrgasmPriapismAphrodisiacsCyclic Nucleotide Phosphodiesterases, Type 2PenisCitric AcidIsosorbide DinitrateSpermatic Cord TorsionAdministration, OralUterine ArteryPlacental CirculationProtective AgentsDouble-Blind MethodCross-Over StudiesHomosexuality, MalePotassium CitrateMethamphetamineNitric OxideInjectionsBlood PressureDose-Response Relationship, DrugGeorgiaHypertension, PulmonaryTreatment OutcomeHeart RateBlood Flow VelocityDrug SynergismOxo-Acid-LyasesCalcium CitrateCarbolinesImpotence, VasculogenicUnsafe SexDogsRisk-TakingClomipheneSexual BehaviorPhosphoric Diester HydrolasesPyrimidinonesTriazines