Viagra was the first drug developed for the treatment of erectile dysfunction. Was engaged in the development, Pfizer (USA) in 1992, the drug used the active ingredient Sildenafil, which gave the international drug name. Today original Viagra is the most popular tool in overcoming sexual impotence. Once in the body, Sildenafil relaxes the smooth muscles of the penis. Simultaneously, ensures strong blood flow to the penis. As a result (during sexual contact) appears erection. Without natural arousal erection Sildenafil causes. Erectile dysfunction can appear in any man because of various reasons. To the development sexual impotence can affect psychological stress, trauma, environmental conditions, etc. Viagra helps to cope with erectile dysfunction of any severity. The massive sales, Pfizer conducted clinical trials of the drug, and in all cases was marked by the highest effectiveness of the product. In addition, it was observed lengthening sexual intercourse and improve its quality.