Prostacel 500 mcg Injection belongs to the class of medicine called vasodilators. It is primarily used in the treatment of erectile dysfunction. Erectile dysfunction, also known as impotence, is defined as the difficulty of keeping a hard and erect penis that is firm enough and suitable for sexual activity. Symptoms may include less sexual desire, trouble getting and keeping an erection, and pain during intercourse. Prostacel 500 mcg Injection is also used as an adjunct to other diagnostic tests in the diagnosis of erectile dysfunction.