An intraurethral pellet of Prostaglandin E1 has been in clinical use for more than ten years. It goes by the trade name Muse© (Vivus Inc.) This is the same medication used for injection, but given by a different route. The injection technique places the medication next to the penile blood vessels. The intraurethral pellet is a much less efficient delivery method. The medicine has to diffuse through the urethral wall into a structure called the corpus spongiosum. In many people, small communications exist between the corpus spongiosum and the principle erectile body, the corpus cavernosum. A small amount of medication often diffuses through these structures and reaches the penile artery where it produces dilation and increased blood flow. Dosages used with the intraurethral pellet range from 250 to 1,000 micrograms. Even with this large dose many people do not respond to Prostaglandin E1 when used by an intraurethral route. Overall, about 30% of patients experience satisfactory rigidity with Muse©.