Intracavernous injections (penile injections) can be an effective alternative for men who do not respond well to oral ED medications like Viagra and Cialis. Some studies show a success rate of 75-80%1, while some doctors report success rates of over 95%.
In order to achieve an erection, the user injects a vasodilator into the corpora cavernosa on the side of the penis. (See our article, “How Do Erections Work?“)
With the proper dosage, the man should achieve an erection in 20-30 minutes, and it should last 1-2 hours.
There is one drug, alprostadil (a form of prostaglandin) which is approved by the FDA as an injectable medication for erectile dysfunction. It is sold under the brand names Caverject® and Edex®. Some men complain that they experience a painful burning sensation when they inject alprostadil.
Many doctors prescribe mixtures of drugs that may be more effective than alprostadil alone, and are less likely to cause uncomfortable side effects.
These mixtures are not available over-the-counter; they are prepared by a formulating pharmacy with a prescription from a doctor. The most common vasodilators combinations are:
Trimix (alprostadil, papaverine, and phentolamine)
Trimix is the most commonly used “combination” injection therapy. It utilizes several different mechanisms to achieve an erection:
- Increasing corporal smooth muscle relaxation
- Decreasing smooth muscle and blood vessel contraction
- Increasing blood vessel dilation
Bimix (papaverine and phentolamine)
Bimix may be prescribed if the effects of Trimix are too strong, or if the patient has adverse reactions to alprostadil.
Quadmix (alprostadil, papaverine, phentolamine, and either atropine or forskolin)
The addition of atropine increases corporal smooth muscle relaxation. Quadmix may be prescribed for men who need something stronger than Trimix.
While these other drugs and combinations are not specifically approved by the FDA for treating ED, they meet the proper “standard of care” for being safe and effective, and may therefore be legally prescribed by doctors. Trimix and Quadmix are generally more effective than Bimix, but they both require refrigeration, and may be more likely to cause side effects.
After prescribing an injectable vasodilator, the doctor will meet with the patient to demonstrate the proper injection technique, using a very small dosage. The doctor will then either schedule follow-up office visits, or provide the patient with instructions to gradually increase the dosage, until a serviceable erection occurs.
The injection is done using a very fine needle on a disposable syringe. The patient fills the needle from a small vial of medicine, and then injects it into the side of the penis. The location of the injection is important; that’s why the doctor demonstrates the correct technique.
The drug should to be injected into the corpus cavernosum, one of the two columns of spongy tissue that run through the penis. The injection site should be in the middle third of the penis at the 10 o’clock (left side) or the 2 o’clock (right side) position.
The patient should only use the minimum amount of medicine required for a serviceable erection. Using too much can result in priapism, a persistent and painful erection. For the same reason, injections should not be combined with oral medications unless you are specifically advised to do so by a doctor. Priapism can cause permanent damage to the penis.
Injections are not a good option for men who have difficulty with fine motor movements, such as men suffering from Parkinson’s diseases, arthritis, etc.
Trimix and other penile injections are very inexpensive compared to oral medications. Depending on the dose required, patients should expect to pay as little as $3 to $6 per use, up to $20 or more per use (depending on the pharmacy and the dose that you require). This includes the cost of the disposable syringes.
Some doctors prefer to deliver syringes pre-loaded with a specific dose and composition of medicine; cost per use may be significantly higher for this service.
Most men have no trouble getting used to using small disposable syringes, which can be purchased in bulk. Men who can’t quite get comfortable with inserting a needle, can use an auto-injector.
Amazon.com recommends the Ambimedinc Inject-Ease Automatic Injector.
According to the site, “Inject-Ease makes injections easy. Simply place your loaded syringe in the Inject-Ease, place the tip against your skin, and press the button to automatically deliver the needle through the skin. You control the rate at which the medicine is injected. The special tip is designed to reduce the sensation of pain at injection. Making injections easier helps reduce anxiety – an independent clinical study showed that 91.6% of participants reported less fear of injections with the Inject-Ease.”
Reasons Why Injections May Not Work
Penile injections are highly effective for most men. When they fail to work, the most common reasons are:
- Improper injection. The needle must be perpendicular to the penis, injected on the side, about 1/3 of the way up from the base of the penis.
- The medication has lost its potency. Be sure the check the expiration date on the medication, and follow the instructions if refrigeration is required.
- A venous leak, which allows blood to drain from the penis, preventing an erection. Venous leaks can be caused by various vascular conditions, some nerve conditions, injuries, Peyronie’s disease, and diabetes. In some cases venous leaks can be corrected by surgery.
Side Effects and Risks
- A painful burning sensation in the penis. This is more common with Trimix and Quadmix than Bimix.
- Bleeding or bruising at the injection site.
- Allergic reactions such as rashes or swelling.
- Priapism, a prolonged and painful erection.
- Needle breakage, which may require surgical removal.
- Scarring and Peyronie’s Disease may result from long-term use of penile injections. The patient should switch the injection site from side to side on the penis, and try to avoid injecting in precisely the same position previously used.
An overdose of an injectable can result in priapism – an erection that won’t go down. This is a dangerous condition that can do permanent damage to the penis. Read our article about priapism for tips on dealing with an erection that persists for more than 2-3 hours.
Penile Injections versus PRP Injection Therapy
Penile injection treatments should not be confused with Platelet-Rich Plasma (PRP) Injection Therapy.
PRP therapy involves injection the penis with platelets and growth factors extracted from the patient’s own blood. It is claimed that this treatment can promote growth and healing in the nerves and blood vessels of the penis. It is not supported by clinical evidence.
- Richter, S; Vardi, Y; Ringel, A; Shalev, M; Nissenkorn, I. “Intracavernous injections: still the gold standard for treatment of erectile dysfunction in elderly men.” International Journal of Impotence Research. Jun 2001; 13(3):172-5.