Medications That Can Cause Priapism and Their Mechanisms

Definition and Types of Priapism

Priapism is a persistent penile erection that continues for more than 4 hours beyond, or unrelated to, sexual stimulation, and is a urological emergency that requires prompt evaluation and management, according to the American Urological Association 1
Ischemic (veno-occlusive, low flow) priapism is a non-sexual, painful persistent erection with little or no cavernous blood flow and abnormal blood gases, and is a true emergency, as stated by the American Urological Association 1, 2
Non-ischemic (arterial, high flow) priapism is a persistent erection caused by unregulated cavernous arterial inflow, often associated with trauma, as reported by the American Urological Association 1
Stuttering (intermittent) priapism is recurrent episodes of ischemic priapism with periods of detumescence in between, according to the American Urological Association 1

PDE-5 Inhibitors, such as sildenafil, tadalafil, and vardenafil, can cause priapism by inhibiting phosphodiesterase type 5, preventing breakdown of cGMP, leading to prolonged smooth muscle relaxation and increased blood flow, as reported by the American College of Physicians 3
Intracavernosal injection therapies for erectile dysfunction, such as papaverine, phentolamine, and alprostadil, can cause priapism, with the highest incidence reported in patients using these therapies, according to the American Urological Association 1

Ischemic priapism is a medical emergency that requires immediate treatment to prevent permanent erectile dysfunction, as stated by the American Urological Association 1