Erectile dysfunction (ED), also called impotence, is the type of sexual dysfunction in which the penis fails to become or stay erect during sexual activity. The active ingredient in Vidalista 10 medicine is Tadalafil. This works in a similar way to Sildenafil, the active ingredient in Viagra, by relaxing the blood vessels and therefore increasing the amount of blood flow in the genitals. Tadalafil works for a lot longer, working up to 36 hours so allows for more spontaneity and does not need to be taken as often.