What Is Kamagra? Sildenafil citrate is an active ingredient in Kamagra 100, which is known as the "blue pill" It is used initially for the treatment of erectile dysfunction (ED), which is also described as impotence, in men. Erectile dysfunction is a condition where a man is unable to achieve and maintain a penile erection adequate for sexual intercourse. It occurs when there is a decreased blood flow to the penis. The reduced blood flow may be due to physical difficulties following an injury o...