Viagra Sildenafil- Originally, the active substance was puristically intended for improving blood flow in the myocardium, treating coronary heart disease and stenocardia. However, it has been proven in several clinical studies that the active substance also has a significant influence on blood flow in the genital organs. Active ingredient increases the folume of blood flowing to the male genitals, shich can casuse a stiff erection in men. read full review »