How does Viagra / Effects work? Viagra in Pakistan (Sildenafil) relaxes the muscles found in the walls of blood vessels and increases blood flow to certain parts of the body, especially an increase in blood flow to the penis that leads to a stronger and longer erection. Viagra tablets in Pakistan are frequently used by men suffering from erectile dysfunction, also known as impotence. It improves your erection if a man is already sexually stimulated (kisses and romance).