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ACEP Now: Vol 43 – No 06 – June 2024

Fresco in Pompeii depicting Priapus, the Greek god of fertility and male genitalia, for whom the condition is named after. (Click to enlarge.)

The presurgical management of ischemic priapism has often involved a stepwise approach, with initial aspiration of blood from the corpus cavernosa to relieve the venous outflow obstruction, followed by intracavernosal injections of a sympathomimetic, usually phenylephrine, if aspiration was unsuccessful. However, data suggest that resolution rates are higher with initial combined strategies (i.e., aspiration and phenylephrine) compared with either alone. In fact, injections of phenylephrine alone (with a 31-gauge needle) are sufficient for some patients. The guidelines state, “Clinicians treating acute ischemic priapism may elect to proceed with alpha adrenergics, aspiration with saline irrigation, or a combination of both therapies, based on clinical judgment.” The guidelines also now recommend that, in patients with prolonged erections after intracavernosal injections of vasoactives for erectile dysfunction, clinicians use intracavernosal injections of phenylephrine as first-line treatment.¹

Phenylephrine is a pure alpha-adrenergic agonist, which can contract the cavernosa smooth muscle and alleviate the venous outflow obstruction of ischemic priapism. The guidelines recommend injection of 100-500 mcg of phenylephrine every three to five minutes because there is insufficient evidence to support an optimal dose. However, several retrospective studies provide insight on how much phenylephrine it typically takes.

One study of 136 cases of priapism in 58 patients revealed that 65 percent were treated with phenylephrine alone, with a median total dosage of 1,500 mcg (range 300–12,000 mcg). Of note, patients with priapism fewer than 36 hours in duration received less phenylephrine (median of 1,400 mcg) compared with those with a duration greater than 36 hours (median 3,500 mcg).⁵ In another study of 74 patient encounters, the median dose of phenylephrine was 1,000 mcg (IQR 500-2000 mcg).6 Despite relatively large doses of phenylephrine, no adverse events or increases in heart rate or blood pressure were reported in either study.^5,6 Although dose adjustments may be prudent in those with significant cardiovascular disease and in pediatric patients, 500 mcg is likely the most efficient initial dose.

The guidance to use phenylephrine up front for most patients may help reduce morbidity by decreasing time to detumescence; however, a plan for an injectable phenylephrine-first approach (plus or minus aspiration) may help with ED efficiency. Clinicians can ensure that the proper phenylephrine concentration (500 mcg/mL or 1,000 mcg/mL, ideally pre-mixed for safety) is available and ready. Further, targeting the initial dose to 500 mcg in most patients may reduce the number of attempts and the time to detumescence.