Priapism: when an erection lasting over 4 hours is an emergency

In short: priapism is an erection that will not go away. The American Urological Association (AUA) defines it as a persistent erection that “continues hours beyond, or is unrelated to, sexual stimulation” (AUA/SMSNA priapism guideline). The type called ischemic priapism traps blood in the penis so fresh, oxygen-rich blood cannot reach the tissue, and the guideline calls it an emergency. The FDA labels for the ED pills and for alprostadil injection all tell men the same thing: if an erection lasts longer than 4 hours, get emergency or immediate medical help. This page explains why, and what to expect when you do.

What is priapism?

Priapism is a prolonged erection that continues long after sexual activity, or starts without any arousal at all, and does not go down. The AUA guideline describes two general types, ischemic (low-flow) and non-ischemic (high-flow), and uses the term stuttering priapism for a recurring form of the ischemic type in which unwanted painful erections come back again and again with periods of normal softening in between (AUA/SMSNA priapism guideline). The drug labels use a time-based shorthand: an erection lasting more than 4 hours counts as prolonged, and the labels for sildenafil, tadalafil and vardenafil describe priapism as a painful erection lasting more than 6 hours (Cialis prescribing information, DailyMed).

Sources: AUA/SMSNA priapism guideline; Broderick et al., J Sex Med 2010, which notes that non-ischemic priapism is largely attributable to trauma. Telling the types apart takes a clinical evaluation, and the guideline says every man with priapism should be evaluated emergently to identify the type (Bivalacqua et al., J Urol 2021).

Why is priapism an emergency?

Ischemic priapism is an emergency because the erectile tissue is starved of oxygen while the erection lasts, and the longer it goes on, the more lasting the damage. The AUA guideline describes blood inside the penis in this state as hypoxic, hypercarbic and acidotic (low in oxygen, high in carbon dioxide, and acidic), and says that left untreated it runs to days or weeks of painful erections followed by permanent loss of erectile function (AUA/SMSNA priapism guideline). The guideline’s summary adds that it “may lead to cavernosal fibrosis,” scarring of the erectile tissue, “and subsequent erectile dysfunction” (Bivalacqua et al., J Urol 2021).

Time matters in a way that is easy to underestimate. The guideline tells clinicians to counsel men whose episode has lasted more than 36 hours that the likelihood of erectile function recovering is low, and the vardenafil label warns that untreated priapism can cause “penile tissue damage and permanent loss of potency” (vardenafil prescribing information, DailyMed).

Which ED treatments list priapism as a risk?

ED medicines taken as a pill, injected or used as a urethral suppository can all cause a prolonged erection. NIDDK lists erections lasting longer than 4 hours among the side effects of ED medicines taken by mouth, by injection or as a suppository, and tells men to call a health care professional right away if it happens (NIDDK, Treatment for ED).

Sources: Viagra, Cialis, vardenafil and Caverject prescribing information, DailyMed. The pill labels give no percentage because the events were rare reports after approval, not counts from a trial, so the rows are not directly comparable.

Even so, the labels frame the risk differently: the pill labels describe priapism as rare or infrequent reports, while in studies of the Caverject injection, which is placed directly into the penis, about 1 in 25 men had a prolonged erection, and the label tells prescribers to warn patients about it. For the full side-effect picture of each pill, see sildenafil side effects, tadalafil side effects and our overview of ED medication side effects. How the three pills differ in other ways is covered in vardenafil vs sildenafil.

What should you do if an erection lasts more than 4 hours?

Get emergency medical care. The tadalafil label says men with an erection lasting longer than 4 hours, “whether painful or not, should seek emergency medical attention,” and the Caverject label says to seek immediate medical assistance for an erection that persists longer than 4 hours (Cialis; Caverject, DailyMed). MedlinePlus is blunter: an erection that does not go away is a medical emergency, and the place to go is the hospital emergency room (MedlinePlus, Penis pain).

Home remedies are not a substitute. The AUA guideline states that conservative measures, which it lists as observation, oral medicines, cold compresses and exercise, are unlikely to work for ischemic priapism and should not delay definitive treatment (AUA/SMSNA priapism guideline). Feeling embarrassed is understandable, but it is not a reason to wait. The guideline tells clinicians to take a medical, sexual and surgical history, so it helps to be ready to say which ED medicine you used, if any, and roughly when the erection started.

What happens at the hospital?

The first job is to work out which type of priapism it is, because the treatment depends on it. The guideline says all men with priapism should be evaluated emergently to tell ischemic from non-ischemic, and that men with the ischemic type should get early intervention (Bivalacqua et al., J Urol 2021).

For ischemic priapism, the guideline’s first-line treatment is draining the trapped blood from the erectile tissue with a needle (aspiration), with or without rinsing it out (irrigation), together with an injection of a medicine called phenylephrine into the penis (AUA/SMSNA priapism guideline). If that fails, the next step is a surgical procedure, called a shunt, that creates a new path for the trapped blood to drain. The guideline stresses that treatment should be based on the patient’s goals, the resources available and the clinician’s experience, so a single pathway is no longer considered appropriate (Bivalacqua et al., J Urol 2021).

Who is more likely to get priapism?

Some conditions make priapism more likely, and the ED drug labels name them. The sildenafil, tadalafil and vardenafil labels advise caution in men with conditions that may predispose them to priapism, such as sickle cell anemia, multiple myeloma or leukemia, and in men with an anatomical deformation of the penis, such as angulation, scarring of the erectile tissue or Peyronie’s disease (Viagra prescribing information, DailyMed). The Caverject label goes further: it says not to use that injection at all in men with those blood conditions, and adds sickle cell trait to the list (Caverject prescribing information, DailyMed).

Having one of these conditions does not mean priapism will happen, and an episode does not by itself point to any of them. It is information for the conversation with whoever prescribes your ED treatment.

Does a painless prolonged erection still need care?

Yes. Pain is not a reliable guide, and the tadalafil label says to seek emergency care for an erection over 4 hours “whether painful or not” (Cialis prescribing information, DailyMed). The high-flow type is usually painless and is not treated as an emergency in the same way, but only a clinical evaluation can show which type a man has, and the guideline calls for every case to be evaluated emergently (Bivalacqua et al., J Urol 2021).

Sources

1. Bivalacqua TJ, et al. Acute Ischemic Priapism: An AUA/SMSNA Guideline. American Urological Association
2. Bivalacqua TJ, et al. Acute Ischemic Priapism: An AUA/SMSNA Guideline. J Urol. 2021;206(5) (abstract, PubMed)
3. Broderick GA, et al. Priapism: pathogenesis, epidemiology, and management. J Sex Med. 2010
4. Viagra (sildenafil citrate) prescribing information, section 5.2, DailyMed
5. Cialis (tadalafil) prescribing information, section 5.3, DailyMed
6. Vardenafil hydrochloride tablets prescribing information, section 5.3, DailyMed
7. Caverject (alprostadil) injection prescribing information, section 5.1, DailyMed
8. NIDDK. Treatment for Erectile Dysfunction
9. MedlinePlus Medical Encyclopedia. Penis pain