A 24-year-old man comes to the emergency department due to a persistent, painful erection that has lasted for more than 8 hours. He had 3 similar episodes in the past 2 years that were less than 30 minutes in duration and resolved with ice packs at home. The patient has had no trauma to the perineal or genital area. He has no other medical conditions and takes no prescription, over-the-counter, or herbal medications. The patient does not use tobacco, alcohol, or illicit drugs. Temperature is 37 C (98.6 F), blood pressure is 124/82 mm Hg, pulse is 84/min, and respirations are 16/min. Examination shows an engorged corpora cavernosa and a rigid, tender penis. The testicles are normal, and the remainder of the examination shows no abnormalities. Penile injection with a medication having which of the following mechanisms would most likely relieve this patient's symptoms?

Question

A 24-year-old man comes to the emergency department due to a persistent, painful erection that has lasted for more than 8 hours.  He had 3 similar episodes in the past 2 years that were less than 30 minutes in duration and resolved with ice packs at home.  The patient has had no trauma to the perineal or genital area.  He has no other medical conditions and takes no prescription, over-the-counter, or herbal medications.  The patient does not use tobacco, alcohol, or illicit drugs.  Temperature is 37 C (98.6 F), blood pressure is 124/82 mm Hg, pulse is 84/min, and respirations are 16/min.  Examination shows an engorged corpora cavernosa and a rigid, tender penis.  The testicles are normal, and the remainder of the examination shows no abnormalities.  Penile injection with a medication having which of the following mechanisms would most likely relieve this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_3c03_192d_9249_e51419f69bdf_MD0001_00 The corpora cavernosa of the penis receive sympathetic innervation (T11-L2) via the superior hypogastric plexus and cavernosal nerves. In the flaccid state, tonic alpha-adrenergic (norepinephrine) sympathetic activity maintains high vascular and trabecular smooth muscle tone, preventing the corpora from engorging with blood. In an erection, activation of parasympathetic nerve fibers (S2-S4) induces relaxation of smooth muscle in cavernous arteries and trabeculae. The increased blood flow fills the relaxed corpora, which subsequently causes compression of the emissary veins against the tunica albuginea, blocking the outflow of blood and further increasing pressure within the corpora cavernosa. This patient has priapism, a painful, firm erection in the absence of sexual stimulus or beyond the normal duration of sexual activity. Priapism is usually idiopathic but can be caused by medications or drugs (eg, trazodone, cocaine) or disease states (eg, sickle cell disease) that disrupt the normal outflow of blood from the corpora cavernosa. Treatment usually includes penile injection of an alpha-adrenergic agonist (eg, phenylephrine), which induces contraction of cavernous smooth muscle; this reduces venous obstruction by the engorged corpora, increasing venous outflow and promoting detumescence. (Choice B) Alpha-1 antagonists (eg, tamsulosin, doxazosin) inhibit tonic sympathetic activity and can trigger priapism. (Choice C) Beta-1 agonists (eg, dobutamine) are positive inotropic agents that increase stroke volume and cardiac output. This will increase blood flow to the penis and worsen priapism. (Choice D) Beta-2 agonists induce trabecular smooth muscle relaxation and increase blood flow to the penis, potentially worsening priapism. Educational objective: The penile flaccid state is maintained by tonic alpha-adrenergic (norepinephrine) sympathetic activity, causing high vascular and trabecular smooth muscle tone, preventing corporal engorgement with blood. Priapism can be treated with penile injections of an alpha-adrenergic agonist (eg, phenylephrine), which induce smooth muscle contraction, leading to detumescence.

A 24-Year-Old Man Comes to the Emergency Department Due to a Persistent