Priapism: When an Erection Won't Go Away

Priapism is the ED medication side effect that generates the most anxiety — and understandably so. An erection that won't go away is a genuine medical emergency. Untreated, it can cause permanent damage and permanent erectile dysfunction. That's the bad news.

The good news: it's extraordinarily rare with PDE5 inhibitors, it's very treatable when caught early, and understanding the warning signs and risk factors can reduce your anxiety to something proportional to the actual risk.

What Is Priapism?

Priapism is a prolonged, persistent erection that occurs without sexual stimulation or continues long after sexual activity has ended. The medically significant type — ischemic priapism — involves blood that flows into the penis but can't flow out. The trapped blood becomes deoxygenated, turning the erection into an oxygen-deprived emergency.

It's important to distinguish this from a normal prolonged erection. If you have a firm erection for 1–2 hours after taking ED medication with sexual activity, that's the medication working. The concern begins when the erection persists for hours after sexual stimulation has stopped and the erection becomes painful — ischemic priapism is typically uncomfortable or painful, not pleasurable.

How Rare Is It With ED Medication?

The incidence of priapism with PDE5 inhibitors taken at prescribed doses is less than 0.1% — fewer than 1 in 1,000 men. In the clinical trial data for sildenafil, tadalafil, and vardenafil, priapism was so rare it was categorized as a post-marketing report rather than a clinical trial finding.

To put this in context: priapism is significantly more common with penile injection therapy (alprostadil/trimix), where rates of 1–3% are reported, and with sickle cell disease, where lifetime risk is 30–45%. With oral PDE5 inhibitors taken as directed, the risk is very small — but not zero, which is why it's worth knowing about.

Risk Factors

Most cases of PDE5 inhibitor-associated priapism involve at least one additional risk factor:

• Sickle cell disease or trait: The single biggest risk factor. Sickle-shaped red blood cells can obstruct venous outflow from the penis. Men with sickle cell disease should use PDE5 inhibitors only under close medical supervision.
• Blood cancers: Leukemia, multiple myeloma, and other hematologic malignancies increase viscosity and can impair venous drainage.
• Combining oral ED medication with penile injections: Using both simultaneously dramatically increases priapism risk. Never combine these without explicit guidance from a urologist.
• Recreational drug use: Cocaine and certain amphetamines can contribute to priapism through their effects on the nervous system.
• Taking more than the prescribed dose: Dose escalation beyond what's prescribed increases all risks, including priapism.

The Damage Timeline

Understanding the timeline helps explain why the 4-hour threshold matters:

• 0–4 hours: The erection is persistent but no permanent damage has occurred. Treatment at this stage almost always results in complete recovery with no lasting effects.
• 4–6 hours: Tissue hypoxia (oxygen deprivation) begins. Smooth muscle cells start to suffer. Treatment is still very effective, but the window is narrowing.
• 6–12 hours: Progressive smooth muscle damage. Edema (swelling) and acidosis develop. Treatment can still work, but the risk of some permanent impairment increases.
• 12–24 hours: Significant smooth muscle necrosis (cell death) begins. Treatment becomes more difficult. Risk of permanent ED is substantial.
• 24–48+ hours: Fibrosis (scarring) replaces smooth muscle. Risk of permanent, irreversible erectile dysfunction approaches 90%.

The message is clear: earlier is always better. Don't wait to see if it resolves on its own past the 3-hour mark.

What to Do: Step by Step

How the ER Treats It

Emergency treatment for ischemic priapism follows a clear protocol. First, the doctor confirms ischemic priapism (as opposed to the non-ischemic type, which is less urgent) by aspirating a small blood sample from the penis — dark, deoxygenated blood confirms the diagnosis.

Treatment involves aspiration (draining the trapped blood with a needle) and injection of a sympathomimetic agent, typically phenylephrine. Phenylephrine constricts the blood vessels, allowing normal outflow to resume. This is usually effective within minutes. The procedure is done under local anesthesia and, while not pleasant, is far less dramatic than most men imagine.

In rare cases where aspiration and phenylephrine don't resolve the priapism, a surgical shunt procedure may be needed to create an alternative drainage pathway. This is uncommon with PDE5 inhibitor-related priapism.

Prevention

• Take the prescribed dose and only the prescribed dose. Never double up because the first dose "didn't work fast enough."
• Don't combine oral ED medication with penile injections unless explicitly directed by a urologist.
• If you have sickle cell disease, use PDE5 inhibitors only under medical supervision with a provider who understands your condition.
• Avoid recreational drugs (especially cocaine) in combination with ED medication.
• If you've had priapism before, inform your provider — a history of priapism increases the risk of recurrence.