Erectile Dysfunction Injections: How They Work

Erectile dysfunction injections sound like the last thing any man wants to try. A needle, in that spot, before sex. But for men whose pills do nothing, they are one of the most reliable treatments urologists have.

Injection therapy puts medicine straight into the erectile tissue, so it can work even when tablets fail. Here is how it works, what the research shows about results and risks, and where pelvic floor training fits alongside it.

What Erectile Dysfunction Injections Are

The technical name is intracavernosal injection therapy. You use a tiny needle to put medicine into the side of the penis, directly into one of the two spongy chambers that fill with blood during an erection.

According to UPMC, alprostadil is one of the main ingredients. It relaxes the blood vessels and smooth muscle of the penis, which lets more blood flow in. Some clinics mix alprostadil with other drugs, but the technique is the same.

Pills like sildenafil work differently. They boost a signal your body has to start first, which is why they need arousal and can fail when nerves or blood vessels are damaged. An injection acts on the tissue itself. For a refresher on that chain of events, see our guide to how an erection works.

Who Usually Gets Them

ED injections are rarely the first step. The NHS lists PDE-5 inhibitor tablets such as sildenafil and tadalafil as the main medicines, alongside vacuum pumps and treating the underlying cause.

Injections come in when those options do not work or cannot be used. UPMC describes them as a good option if oral medicines do not work for you, or if health issues or other medications rule tablets out. Men with diabetes or those who have had their prostate removed are often considered harder to treat, and injections remain an option for them. If you have not had a proper workup yet, start with our guide on how to check for ED.

How Well Do ED Injections Work?

The results are strong, which is why urologists keep offering them despite the needle.

• UPMC reports a success rate of 70 to 80 percent. It notes injections may not work if blood flow in the penis is low.
• Long-term users stay satisfied. In a 2020 study in the International Journal of Impotence Research, Bearelly and colleagues followed 105 men who had used injections for an average of 8.4 years. Patient-reported penile rigidity rose from about 41 percent before treatment to about 90 percent on injections.
• Hard-to-treat men did just as well. That study found no difference in questionnaire results between men with diabetes or prostate removal and everyone else.

That last point matters. The men for whom pills most often fail are the ones injections still help.

How the Injection Is Done

Your first dose happens in the clinic. The UK prescribing information for alprostadil says first injections must be done by medically trained staff, and the dose is set for each man through careful testing under a doctor's supervision.

After that, you inject at home. The basics:

1. Use the right needle. The label recommends a half-inch, 27 to 30 gauge needle, which is very fine.
2. Inject into the side, near the base. The label places the usual site on the upper side of the shaft, in the third closest to your body. Avoid visible veins, and alternate sides and spots each time. Your clinician will show you the exact area.
3. Use the lowest dose that works. The label notes most men respond to 5 to 20 micrograms, and doses above 60 micrograms are not recommended.
4. Respect the frequency limit. The usual maximum is once a day and no more than three times a week, with at least a day between doses.

UPMC adds that if you are not comfortable injecting yourself, a partner can learn to do it.

Side Effects and Risks

Injections are effective, but they come with trade-offs you should know before you start.

Penile pain. This is the most common reaction to alprostadil. The UK label says 30 percent of men reported pain at least once, though it followed only 11 percent of injections.

Bruising and curvature. In the Bearelly study, 7.6 percent of men had bruising and 10 percent developed mild curvature of under 30 degrees. UPMC also warns that scar tissue can form at the injection site.

Prolonged erection. The same study reported priapism in 7.1 percent of men. If an erection lasts 4 hours, get medical help. The alprostadil label says treatment should not be delayed beyond 6 hours, since prolonged erections can damage tissue.

Who should not use them. The label rules out men with penile implants and those with conditions that raise priapism risk, such as sickle cell anaemia. UPMC adds that men whose heart health is not stable enough for sex should not use them. It also warns that combining alcohol with ED medicine can cause a serious drop in blood pressure.

Where Pelvic Floor Training Fits

Injections create an erection on demand. They do not change the muscles that help you hold one. That is where kegels come in.

Two pelvic floor muscles, the bulbocavernosus and ischiocavernosus, press on the base of the penis during an erection and help keep blood from draining out. In a randomized trial in BJU International, Dorey and colleagues studied 55 men with ED. Men taught pelvic floor exercises by a physiotherapist, plus lifestyle changes, did significantly better than men given lifestyle advice alone. After 6 months, 40 percent had regained normal erectile function and another 35.5 percent had improved.

That does not mean kegels replace injections for a man with severe nerve damage. It means training is a low-risk habit worth building whatever treatment you use. Our guide to ED treatment options compares the full range.

Questions to Ask Your Urologist

If injections come up, these questions will help you decide:

• Why are injections a better fit for me than tablets or a pump?
• Which medicine or mix will you use, and how will we find my dose?
• What should I do if an erection lasts too long, and where do I go?
• How do I avoid scar tissue and curvature over time?

A good urologist will expect these questions. If you want to find one who specializes in ED, see our guide to urologists for impotence.

The Bottom Line

Erectile dysfunction injections work for most men, including many for whom pills have failed. The main costs are the needle, some pain or bruising, and a small but real risk of prolonged erection that needs fast treatment. Pair whatever treatment you choose with steady pelvic floor training, and ask your urologist about your own risks before you start.