Nonischemic priapism is usually associated with pelvic trauma. Cavernous blood gas obtained at the time of the event can help distinguish between the 2 types. The color of the aspirated blood sample is black in patients with ischemic priapism. Corporal blood gas analysis shows hypoxemia and acidemia. The color of blood is red in patients with nonischemic priapism and shows normal oxygen and pH. Priapism is a urologic emergency requiring aspiration of blood from the cavernous sinus to prevent ischemic tissue damage. At times surgical decompression may be required if aspiration is not successful.
Adrenergic α-blocking agents were developed for treatment of hypertension. They have become popular for management of lower urinary tract symptoms (LUTS) secondary to prostate enlargement. Doxazosin, prazosin, and terazosin are nonuroselective and have a higher risk of cardiac adverse effects (AEs), including dizziness and orthostatic hypotension. Lexicomp lists < 1% incidence of priapism associated with doxazosin.9 The drug is metabolized by CYP3A4 with secondary pathways, including CYP2D6 and 2C9 with a drug half-life of 22 hours. Newer agents (eg, tamsulosin, alfuzosin) are considered more uroselective, targeting the α-1b receptors. The older agents have more effect on the α-1a receptors, which are also present at higher level in the cardiovascular system.10 By blocking sympathetic stimuli responsible for penile detumescence, the nonselective α blockers have a higher propensity to cause priapism. There seems to be a direct correlation between higher doses and increased risk of priapism.11 Our patient was at a relatively low dose (1 mg twice daily) of the nonselective agent doxazosin for treatment of his LUTS.
Primary care providers and psychiatrists treating depression are familiar with common sexual AEs of the SSRI class of medications. Decreased sexual desire and delayed orgasm and ejaculation are all issues that lead patients to discontinue treatment. Although SSRIs are considered first-line treatment for depression, reports indicate that up to 60% of patients with prior normal sexual function started on paroxetine may experience sexual AEs.12 The exact frequency is difficult to estimate due to underreporting of these issues by patients.
A review of the literature for cases of priapism associated with SSRIs shows that often there is more than 1 possible drug trigger, and medications used in combination may be a risk factor. It is hypothesized that SSRI action on 5-HT3 receptors may be responsible for priapism occurring in patients treated with SSRIs.13 One study cites a case of priapism in a veteran being treated with escitalopram, prazosin, and trazodone for posttraumatic stress disorder.14 Trazodone inhibits the neuronal uptake of serotonin and is used to treat depression in addition to off-label use in treatment of insomnia. Trazodone is implicated in cases of priapism via its α-blocking properties. In the aforementioned case, trazodone was initially thought to be the causative agent and was discontinued. The patient had recurrent symptoms at which time his prazosin was discontinued, and he had no further events.
Another case cites citalopram-induced priapism that occurred with an accidental overdose of citalopram 80 mg, when a patient confused his antidepressant with 81-mg aspirin tablets.15 He also had a prior history of priapism while taking trazodone. We found only 1 case listing escitalopram as the probable causative agent of priapism.16 Similar to our patient, that case had no risk factors prior to escitalopram administration. Lexicomp notes < 1% incidence of priapism reported in postmarketing studies.
Our patient had been off doxazosin for 18 days when his second event of priapism occurred. It is less likely given the half-life of doxazosin (t ½ = 22 hours) that the α blocker was the causative agent, though a combination of the 2 agents cannot be excluded as a significant factor. The Naranjo Score is an algorithm for determining the likelihood of whether an adverse drug reaction is due to the drug or other factors.17 Scoring ranks the event as probable, possible, or doubtful. This case scored +3 (+2 = appeared after suspected drug given, +1 = improved when drug discontinued), indicating possible association of escitalopram and priapism.
Conclusion
In view of the frequent use of SSRIs in treatment of depression, it may be prudent to advise patients of this uncommon but serious medication AE. Recent use of α blockers may be a risk factor in combination with SSRI therapy. Patients should be counseled to seek emergency care in the event of prolonged erection when discussing potential AEs of SSRI therapy.