Article by Patrick M. Carpenter, MS, PharmD, RPh
Syringe and Dose
Penile Injections for treatment of ED are called intracavernosal injections (ICI), because you inject within the corpus cavernosum – the erectile tissue of the penis.
Oral medications including tadalafil (Cialis) and sildenafil (Viagra) are the first line therapy for the treatment of erectile dysfunction. If oral meds work for you, there is no reason to consider injection therapy. However, in cases where the oral medications cause intolerable side effects, or if oral medications do not work, penile injections are a proven and effective treatment option.
Injection Liquid Formulations
The injection liquid is most commonly a mixture of two or three medications in a sterile vial. The possible medications are alprostadil (sometimes called prostaglandin E1, or PGE1), papaverine, and phentolamine. Mixtures of all three ingredients are commonly referred to as trimix, while mixtures of just papaverine and phentolamine are commonly referred to as bimix.
Bimix comes in various concentrations. These formulations are comprised of (papaverine/phentolamine)/mL respectively, and listed here in order of weakest to strongest:
Trimix is comprised of (alprostadil/papaverine/phentolamine)/mL respectively. We generally put trimix in categories based on ‘standard’ concentrations or ‘low alprostadil’ concentrations. Alprostadil causes an aching sensation in the penis in about 20% of men who use it. Although it is harmless, the pain may interfere with enjoyment of the erection, and your doctor may change your prescription to a low alprostadil trimix. Here are the available standard and low alprostadil concentration groups also listed in order from the weakest to the strongest within each group:
Low Alprostadil Trimix
Syringe and Dose Volume
ICI medications are injected into the penis using a very small needle, the same type of needle and syringe diabetics use to inject insulin. The syringe is the plastic part of the device that holds the liquid. Printed gradations on the syringe allow you to measure a certain volume (amount) of liquid (your dose). Syringes are available in 3 different volumes: Syringes that hold 30 units (0.3mL), 50 units (0.5mL), and 100 units (1.0mL). A milliliter (mL) is the same as a cubic centimeter (cc) so you may see both abbreviations.
The needle is the shiny silver part of the device that punctures the skin. The needle sizes vary in two dimensions, gauge and length. Gauge refers to the thickness of the needle (the diameter). Common gauges for penile injection, in order of thickest to thinnest are 27 gauge, 29 gauge, 30 gauge, and 31 gauge. 31 gauge is the thinnest needle in this example and 27 gauge is the thickest. All of these gauges are very thin needles. You might be thinking you want the thinnest needle, but the thinner the needle is, the more likely it will bend.
The most common needle lengths for penile injection are 5/16-inch (8mm) or ½-inch (12.7mm). You might be thinking you want the shortest needle, but your doctor may have chosen a specific length based on how you were trained and your anatomy and/or pathology. The injection technique may vary slightly based on the length of the needle. You shouldn’t think of the 2 length options as interchangeable without some coaching. Your doctor may have a strong preference for the type of needle you should use based on the doctor’s experience or your anatomy and/or pathology.
Your Physician Will Establish Dose Volume
Your doctor will indicate a starting injection volume for you and may give instructions to increase or decrease the amount of medicine based on your response. You may have been given a test dose in the doctor’s office, or the doctor may have trained you in the office, and you gave yourself your first dose there. Based on your response in the office your doctor will make a decision about what strength of medicine (concentration) and what dose (volume of injection) you should administer at home. It’s important to follow your doctor’s instructions and be sure you understand the dose. Many people get confused about units vs. milliliters vs. cubic centimeters.
Injection technique can vary. In fact, over time it is important to rotate injection sites to avoid repeated puncture in the same location that could lead to scar tissue formation. In the following sections I describe one technique we recommend to patients when they get started on injection therapy. The goal is to minimize variability in injection technique, allow you to focus on learning to do the injection properly, and to adjust the dose over time to produce an erection sufficient for intercourse.
Wipe the top of your vial with an alcohol wipe to disinfect the stopper. Wipe the side of your penis where you intend to inject to disinfect your skin.
Proper Injection Site
Stand up. Hold the head of your penis in one hand and lift it, if needed, so that it is pointing straight out in front of you. In terms of the length of your penis you will inject right in the middle, that is, halfway between the base (your body) and the tip (the head of the penis) – or a little closer to your body. Do not inject anywhere near the head or the tip of the penis. For example, if your flaccid penis is 3-inches long you will inject 1 to 1.5-inches away from your body. If your flaccid penis is 4-inches long you will inject 1 to 2-inches away from your body.
In terms of the circumference of your penis, that is, around your penis, imagine your penis is like the face of a clock. You want to inject directly in the side at 3 o’clock or 9 o’clock.
If you are using a 5/16-inch needle you should insert the entire needle into the side of the penis. The area where the shiny silver needle meets the plastic of the syringe is called the “hub.” The hub should make a small indent in the side of the penis during injection when using a 5/16-inch needle.
If you are using a ½-inch needle insert the needle, but do not create an indent with the hub. Alternatively you should leave 1-2 millimeters of the shiny silver needle showing when using the ½-inch needle. Think of the thickness of a dime. The thickness is the side of the dime, the distance from the heads side to the tails side or about 1.3mm. So if you are using a ½ inch needle most of the needle should enter your penis, but it is okay to leave the equivalent of the thickness of a dime showing of the shiny silver needle.
After the needle is inserted begin to depress the plunger. Take 1-2 seconds for every 10 units of fluid you inject. For example, if you are injecting 30 units that means you depress the plunger for 3-6 seconds. Once the plunger is fully depressed you can withdraw the needle from the side of your penis.
Apply Light Pressure
After withdrawing the needle place your thumb over the injection site and gently squeeze the skin between your thumb and forefinger. Keep this light pressure on the penis at the injection site for 1-2 minutes. The pressure will minimize bruising and bleeding and is thought to minimize scar tissue formation. After 2 minutes of pressure it is time to wait for the erection, which may be developing already and if not should begin to develop in another 3-8 minutes.
Adjust Your Next Dose (if needed)
If this is one of the first times that you have injected, the erection that develops may not be perfect and may be too soft for penetrative sex. See my earlier blog post Willing to Put in the Work for reminders that learning a new skill, like injecting into your penis, and perfecting the dose will take some practice. If this erection isn’t perfect and your doctor has indicated on the prescription that you can increase your volume of injection, then plan to try again in 24-hours and go to the next recommended volume of injection. In office training by your physician helps minimize the learning curve for self-injection first timers. Online resources are also available, including videos, and written guides with illustrations.
It is important not to inject more than once every 24-hours, and most doctors recommend not injecting more than 3-4 times weekly to minimize scar tissue formation. Like most therapies there are certain risk factors and side effects, but overall, injection therapy is extremely well tolerated. Bleeding, infection, and scarring are all possible, but with proper technique and counseling they are manageable. If any of these side effects happen, seek immediate medical attention.
Priapism is an erection lasting more than four hours and is also a risk factor. By starting at a lower dose and slowly working up on the dosage priapism is preventable, however if you experience priapism or a painful erection seek immediate medical attention at your nearest emergency department.
Storage recommendations may vary from one pharmacy to another based on the testing and data the pharmacy compounding the medication has collected relating to their specific production process and formulation. ICI medications distributed by PharmaLabs, menMD’s pharmacy source, have the following storage conditions: Bimix and Trimix must be refrigerated. The alprostadil component of trimix is sensitive to degradation by heat. The warmer it is the faster it becomes inactive.
Bimix and trimix should not be used longer than indicated by the “Beyond Use Date” on the label of your medication. “Beyond Use Date” is the term compounding pharmacies are required to use to mean “Expiration Date.” For bimix the beyond use date will vary based on when the product was compounded and when your prescription was dispensed. The beyond use date for an unpunctured bimix vial can be from 30-165 days. Once you puncture the vial it should not be used longer than 28 days after you first puncture it. For trimix, due to the delicate nature of alprostadil the beyond use date for an unpunctured vial is 30 days. Once you puncture the vial it should not be used longer than 28 days after you first puncture it.
Anxiety is Normal
The idea of putting a needle into your penis may sound daunting, but hundreds of thousands of men have done this before you. ICI has been used for the treatment of ED since the early 1980’s. The most reluctant injectors have called our clinical department after achieving success with the medicine to say things like, “I feel like a man again,” or, “Thank you for the encouragement, this therapy has saved my relationship.” The idea of the injection, merely contemplating it, is the most difficult part. The injection itself once you perfect your technique is nearly painless.
There are also a variety of tools and assistance devices aimed at addressing the needs of people using ICI therapy. There is a travel bag, called an Insul-tote, which has a small reusable ice pack and pockets for the vial of medication and syringes. There is an Auto Injector device that can help hold the syringe and will insert the needle into the penis all hidden from view. The Auto Injector is good for people who have shaky hands or are very intimidated by the sight of the needle. There is a magnifying device called Insul-Ease, if you have trouble reading the gradations on the syringe, which will allow you to be sure you are measuring the right dose. Lastly you should purchase a Sharps Container so you have a safe place to dispose of the syringes/needles after your injection. All of these accessories are available through menMD and dispensed by PharmaLabs.
We’re Here to Help
If you have questions about your treatment plan, menMD’s clinical case managers are available to help. Please call us at (857) 233-5837 or go online to menMD.com/portal to chat live.