Penile Injections: A Patient Guide

Although you probably find the idea of injecting something into your penis unappealing, many men are highly satisfied with this therapy and will testify to the ease and effectiveness of the injections. Before using the therapy on your own at home, your doctor will show you how to inject the medication. Improper injection and any subsequent scarring can lead to penile curvature and nodules in the penis, so it is important to get proper training before beginning injection therapy.

How medication is injected

The medication is injected along either lateral side of the penis. First, the medication is drawn into a syringe, usually an insulin-type syringe with a short, very fine needle. The medication is given into the spongy tissue of the penis, called the corpora cavernosa.

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After choosing the proper site to inject on your penis, clean it with an alcohol wipe, “poke” the needle through the skin of the penis, and then inject the medication into the penis. Immediately afterwards, press firmly on the injection site with either an alcohol pad or gauze with your thumb and first finger to compress the area for at least five minutes or up to 10 minutes for patients taking blood thinning medication, such as coumadin.

The medication tends to work better if you stand, as it allows more blood to go to your penis. Also, external stimulation to the penis increases blood flow to the penis and allows the medication to take effect faster.

Some people prefer the auto-injector, which is a spring-loaded device that inserts the needle into the penis very quickly, minimizing discomfort and psychological “hesitancy.” It comes in two forms: a simple, non-prescription device designed to insert the needle for you, and a prescription device that also depresses the plunger for you.

Check with your local drug store for the non-prescription simple auto-injector. Many men prefer the auto-injector that does not inject the medications for them, because they maintain the necessary feel to know that they have injected in the right place and to the right depth.

Side effects

Occasionally, penile injections can cause fainting, dizziness and low blood pressure. In rare instances, priapism or prolonged erections can occur. Patients who are not trained properly may experience pain, infection, bruising and scarring.

Things to remember

• After inserting medication, self-stimulation may be necessary to increase blood flow to your penis.
• If your erection persists for more than four hours, seek medical care at a local emergency room or from your urologist.
• Penile injections may be ineffective in patients who have vascular disease or blood flow problems.

General FAQs

Do penile injections work for everyone?

If the medication is dosed and injected properly, most men will experience an erection response to injections. Finding a dose that works typically requires making adjustments early on. Some men, however, don’t respond even to high doses.

Are there medical conditions that preclude using penile injections?

Injections aren’t an option for men with any of the following:

• Severe scarring of the penis
• Active infection or sores on the penis
• Allergies to the medications used for injection

Men who are allergic to one of the medication options may be able to use an injection agent that doesn’t contain the allergen.

Can I use injections if I take a blood-thinning medication, such as aspirin, clopidogrel (Plavix) or warfarin?

Yes. While blood thinners increase the risk of bleeding and bruising, the needles used for penile injections are small. The risk is minimal so long as you apply pressure on the site immediately after giving yourself an injection.

If I have a condition that causes blood flow problems, such as diabetes, would injection therapy help with erections?

Injections are a powerful treatment but don’t work for everyone. Men who have severe or long-standing diabetes have less chance of success with injections. The only way to find out, however, is to try them.

After a nerve-sparing prostatectomy, will injections help me recover natural erections?

Some experts believe that inducing erection responses – a process that injections support – can help preserve or restore natural erections. Though that remains a theory, there’s little risk in trying, as long as you do the injections correctly. (Regardless of their value in penile rehabilitation, erectile dysfunction medications can help patients achieve erections for sexual activity after prostate cancer treatment.)

What’s the optimal time after prostatectomy to begin injection therapy?

There’s no strict criteria for when to start. Most men should take at least four to six weeks to recover from the operation before resuming sexual activity, including use of penile injections.

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Will injections work on men who had non-nerve-sparing prostatectomies?

One advantage of injections is that they bypass the nerves that induce erections under normal circumstances. For this reason, injections usually work regardless of nerve-sparing status.

Are the recommendations for using penile injections different when erectile dysfunction (ED) results from radiation therapy, as opposed to other causes?

No, the recommendations are the same.

Can injections be used with vacuum erection devices, or penis pumps?

It is neither necessary nor advisable to use a vacuum device in conjunction with injections. The risk of bruising or bleeding increases if you apply a vacuum device.

I was told not to do more than two injections a week. What’s the reason I can’t inject every day, for example?

The risk of scar tissue rises with each injection. We don’t fully understand this process, but hypothetically, frequent injections increase the risk of scar tissue buildup. Some experts therefore recommend avoiding “overly frequent” dosing. What that means is subject to interpretation, so you should discuss this safety concern with your doctor.

If an injection doesn’t start working in 15 minutes, can I try another injection?

No. Repeat dosing isn’t recommended because it can cause priapism, a prolonged erection that’s potentially dangerous.

Medication FAQs

What medications are used for injections? What are their differences?

There are several medications that can work to help you achieve erections. You and your doctor should discuss which is likely to be best for you. The drugs and drug combinations currently in use include the following:

• Papaverine is available at a relatively low cost and is stable at room temperature, but it’s less effective than the other options and may be more likely to cause scarring (fibrosis).
• Papaverine plus phentolamine (Bi-Mix) is more potent than papaverine alone, but with the same potential side effects, such as priapism and scar tissue formation.
• Alprostadil rarely causes priapism, but it may cause pain. (Alprostadil is also known as prostaglandin E1. In powdered form, it may be called CaverJect or Edex.)
• Papaverine plus phentolamine plus alprostadil (Tri-Mix) is the most potent option. It requires refrigeration and has the same side effects as papaverine and alprostadil.
• Quad-Mix, a combination of Tri-Mix and a drug called atropine, is another formulation, but it’s not often used, as the role of atropine in the erection process is unclear.

If you’re using injections but having problems achieving adequate erections, talk to your health care provider about changing the medication, the amount you inject or the strength of the solution.

How do these medications work to produce an erection?

The drugs lead to an erection by relaxing the smooth muscles and widening the blood vessels in the penis, enhancing blood flow. They don’t depend on nerve stimulation. A more complete description of how the penis functions can be found in our discussion of erectile dysfunction.

How is the correct dosage determined? How do I know when I’m on the right dose?

Dosage involves the medication’s strength and the amount used. With the appropriate strength and amount (usually less than 1 cc), as determined by a doctor, erections usually occur in five to 10 minutes and last approximately 30 minutes to an hour. The erection becomes more rigid if sexual stimulation occurs. It may take some time and experimentation to determine your optimal medication and dose.

Will I develop a tolerance over time and require an increasing dose?

You won’t develop a tolerance, but since ED is progressive, dose adjustments over time are sometimes necessary, particularly for men who use injections for many years. You may be able to reduce the need for this by compressing the site after injecting, switching up your injection placement and spacing out your injections.

My medication requires refrigeration. How long can it be left out?

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The issue isn’t that the medication will spoil and become dangerous, as with food left out of the refrigerator. But these drugs gradually lose potency, a process that accelerates if they’re not kept cold. So try to put your medication back in the fridge promptly.

Can I use the medication directly from the refrigerator?

Yes, so long as it’s completely thawed (not frozen).

Are there medications not requiring refrigeration that I can use while traveling?

Some medications are available in powdered form to be mixed at the time of use. Examples include alprostadil (CaverJect or Edex) and some formulations of Tri-Mix. Mixed compounded medications can be transported but ideally should be kept in checked bags or a cooler, so they stay as cold as possible and retain potency.

Do these medications lose potency over time even if stored correctly?

Yes, over several months they become less effective. Compounding pharmacies are required to note expiration dates for their products. The medication won’t become dangerous to use after expiration but may be less effective.

Are there long-term side effects to the use of injections?

There is a small risk that injections or medications used can cause or reveal scarring in the penis. This can lead to Peyronie’s disease, a painful deformity of the penis caused by a build-up of plaque or scar tissue in the erectile tissue (the corpus cavernosa). However, Peyronie’s Disease is relatively rare and can be treated. You can minimize the risk of developing Peyronie’s disease by using correct injection technique.

Are there medications that reduce the risk of Peyronie’s disease?

No medical therapies are shown to reduce the risk of developing Peyronie’s disease. Some experts recommend using certain drugs (such as pentoxifylline, which improves blood circulation), but we don’t have robust evidence that these drugs work for this purpose.

Can compressing the injection site reduce the chance of Peyronie’s?

Compressing the site to prevent bleeding may reduce the chance of developing scar tissue.

Injection FAQs

How can I easily withdraw the medication from the upside-down glass vial?

Before piercing the rubber top of the vial, pull back on the syringe plunger to draw in a volume of air roughly equivalent to the amount of fluid you plan to inject. Keeping this air in the syringe, push the needle through the rubber stopper on the medication vial. Holding the vial upside-down, press the plunger to push the air into the vial before withdrawing the medication dose.

Where in the penis should the medication go? What structures do I aim for and which do I avoid?

You need to inject into the corpora cavernosa (columns of spongy erectile tissue running the length of the penis). Alternate between injecting at 3 o’clock and 9 o’clock positions at the middle of the shaft. Avoid any area where a blood vessel is visible, and don’t inject the same spot every time.

Besides the 3 and 9 o’clock positions, I’ve been told that I can inject at 2, 4, 8 and 10 o’clock. Does it matter?

These alternative positions are OK, but there’s a greater risk that the needle won’t go into the erectile tissues, leading to a failed injection.

How can I be sure I’m injecting in the right place?

The key is to ensure that the needle gets into the corpora cavernosa. This is best accomplished by inserting the needle perpendicular to the penis shaft. You may note a small amount of resistance as the needle penetrates your skin and again when it penetrates the tunica albuginea (the tough sheath covering the erectile tissue). If the needle is properly placed, it shouldn’t be difficult to push down on the plunger. If you meet resistance, the needle tip may be in a tough layer of fascia; in this case, back up the needle slightly and try again.

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