Priapism: What the Viagra and Cialis Labels Say About Long Erections

This page explains what priapism means, what the ED pill labels say, who is at higher risk, and what happens at the hospital. It does not tell you how to treat it yourself, because there is no safe way to do that at home.

Priapism meaning

MedlinePlus, the US National Library of Medicine's health site, defines priapism as "a painful erection that does not go away" (MedlinePlus: penis disorders, read 14 November 2026).

The urology guideline is more exact. It calls priapism "a persistent penile erection that continues hours beyond, or is unrelated to, sexual stimulation and results in a prolonged and uncontrolled erection" (AUA/SMSNA guideline, J Urol 2021, PubMed). The AUA is the American Urological Association.

There are two main kinds. In ischemic priapism, blood is trapped in the penis and cannot get out, so the tissue runs short of oxygen. The guideline says this kind "represents a medical emergency and may lead to cavernosal fibrosis and subsequent erectile dysfunction". Fibrosis means scarring of the spongy tissue that fills with blood. The rarer kind, non-ischemic priapism, is usually painless. A doctor tells the two apart; you cannot do it yourself.

Erection lasting more than 4 hours: the label rule

Both ED pill labels use the same 4-hour line.

The Viagra (sildenafil) label says: "In the event of an erection that persists longer than 4 hours, the patient should seek immediate medical assistance. If priapism is not treated immediately, penile tissue damage and permanent loss of potency could result." (DailyMed: Viagra label, read 14 November 2026). Potency here means the ability to have erections.

The Cialis (tadalafil) label says: "Priapism, if not treated promptly, can result in irreversible damage to the erectile tissue. Patients who have an erection lasting greater than 4 hours, whether painful or not, should seek emergency medical attention." (DailyMed: Cialis label). Note the words "whether painful or not". A painless erection that lasts too long still counts.

How common is priapism on ED pills?

Rare. The Viagra label says long erections and priapism "have been reported infrequently since market approval of VIAGRA" (Viagra label). The Cialis label says "There have been rare reports of prolonged erections greater than 4 hours and priapism" for this class of drugs (DailyMed: Cialis label). Neither label gives a rate, because these come from reports after the drugs went on sale, not from trials.

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) lists it among the problems that need fast care. It says ED medicines "can have side effects, including erections that last longer than 4 hours, known as priapism" (NIDDK: ED treatment, read 14 November 2026). That covers pills, injections and suppositories.

Who is at higher risk

Both labels name the same groups. The Cialis label asks for caution "in patients who have conditions that might predispose them to priapism (such as sickle cell anemia, multiple myeloma, or leukemia), or in patients with anatomical deformation of the penis (such as angulation, cavernosal fibrosis, or Peyronie's disease)" (DailyMed: Cialis label).

In plain words:

• Blood conditions. Sickle cell anemia, multiple myeloma and leukemia can make blood thicker or stickier.
• A bent or scarred penis. Peyronie's disease causes a bend from a hard lump of scar tissue.
• Taking more than prescribed, or two ED drugs at once. The labels say combinations with other ED treatments have not been studied.
• Injections for ED. The 2022 urology guideline covers "prolonged erection following intracavernosal vasoactive medication", meaning drugs injected into the penis (AUA/SMSNA guideline, J Urol 2022, PubMed).

Tell the prescriber about any of these at the online visit. Every intake on a licensed program asks about blood disorders and the shape of the penis for this reason.

Priapism treatment: what happens at the hospital

Treatment is done by emergency doctors and urologists, not at home. The guideline says "All patients with priapism should be evaluated emergently to identify the sub-type of priapism (acute ischemic versus non-ischemic) and those with an acute ischemic event should be provided early intervention" (AUA/SMSNA guideline, J Urol 2021, PubMed).

The guideline does not set one path for everyone. It says "some men may be treated with intracavernosal injections of phenylephrine alone, others with aspiration/irrigation or distal shunting". In plain words, a doctor may inject a medicine into the penis to shrink the blood vessels, drain the trapped blood, or in some cases operate. Which one depends on the type of priapism and how long it has lasted.

Time matters most. The longer blood stays trapped, the higher the risk of lasting damage. That is why the labels say "immediate" and "emergency", not "call your doctor next week".

What to do if an erection will not go down

• At 4 hours, go. Go to an emergency room or call emergency services. Do not wait to see if it settles.
• Say what you took. Tell staff the drug, the time you took it, and any other medicines or drugs.
• Do not take more. Never take another ED pill or try a home remedy.

Can you still use ED pills after priapism?

That is a question for a urologist. Some men can, at a different drug or strength; others cannot. Our ED pill side effects guide covers the other label warnings, and how long Viagra lasts explains the normal timing, which is a few hours, not most of a day.

Prescribers who answer follow-up questions

Many online ED programs let you message a clinician after the visit, which helps when a side effect worries you. This table is from each program's own pages.

From each program's own page, read 2026-11-02.

Generic sildenafil starts at $1.60 a dose at Strut Health, visit included, as checked November 14, 2026. Every program is ranked on Best online ED programs, and all prices are on our ED cost page.