Intracavernous Penile Injections for Erectile Dysfunction


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.

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.

Many of the vasodilators used for penile injection therapy are not available over-the-counter; they are prepared by a formulating pharmacy with a prescription from a doctor. The most common vasodilators are:

Bimix (papaverine and phentolamine)

Trimix (prostaglandin, papaverine, and phentolamine)

Quadmix (prostaglandin, papaverine, phentolamine, and either atropine or forskolin)

There are also pre-formulated commercial vasodilators, such as Caverject® and Caverject Impulse®

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. (Caverject Impulse is supplied in pre-filled syringes.) The location of the injection is important; that’s why the doctor demonstrates the correct technique.

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. Priapism can cause permanent damage to the penis.

This is 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 $15-18 per use.  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.

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.

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.


  1. 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.

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