[Viagra: oral therapy of male erectile dysfunction I]

Sildenafil, the active component of Viagra was synthetized in 1992-3 and registered for sale in US and subsequently in Europe in 1998, on the basis of positive results of numerous preclinical and clinical studies. In the first part of this review, male sexual impotence (recently named erectile disfunction) is defined and its history and epidemiology is reported. The anatomy, physiology and biochemistry of erectile disfunction and the cycle of male sexual response are also discussed.