Injection therapy for erectile dysfunction can be intracavernosal or intraurethral. Agents used include alprostadil for both intracavernous and intraurethral or papaverine phentolamine for intracavernous injection. The mechanism involves vasodilation of the arteries and veins leading to corporal smooth muscle relaxation and penile erection. Priapism is the most critical complication as prolonged engorgement can lead to ischemia. Treatment of priapism consists of emergent urologic consult, narcotic analgesia, and injection of terbutaline, 0.25–0.5 milligrams subcutaneously into the deltoid, repeated in 30 minutes if needed. If this fails, corporal irrigation with phenylephrine or plain saline is required. If this fails as well, surgery may be required. Sickle cell patients with priapism require simple or exchange transfusion.