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From Start to Finish: Understanding the Duration of a Penile Injection

Jun 2, 2023
From Start to Finish: Understanding the Duration of a Penile Injection

The American Urological Association considers penile injections to be one of the most effective non-surgical solutions for treating erectile dysfunction (ED).1 These safe and effective treatment options have been used since 1983.

Trimix injections are a compounded prescription medication that can increase the benefits and reduce the side effects of penile injections by using lower doses of three medications that work synergistically. Trimix injections are expected to help men achieve an erection for about 30 minutes, though results can vary.

Why do men choose penile injections?

An estimated 30 million men in the United States and 150 million men worldwide are affected by ED. There are many risk factors, but most involve the cardiovascular system. The degree of ED a man experiences seems to be a marker for the severity of cardiovascular disease. Symptoms of ED generally precede symptoms of cardiovascular disease by about five years.2

Oral ED medications dilate blood vessels. Men with medical conditions that affect blood flow into the penis may find that oral ED medications do not work well for them, and penile injections may be a better solution. Other reasons men may choose penile injections over oral medications include the following: side effect profile, contraindications to oral medications, ease of use, and a lack of systemic effects.

How often can you do penile injections?

Penile injections are administered into the side of the penis using a short, very fine needle. The medication is quickly injected into a cavernous space on the side of the penis, and pressure is applied for at least 5 minutes. This reduces the risk of bruising and scarring.

In most cases, penile injections begin to work in 10 to 15 minutes. Standing and externally stimulating the penis can speed up the process because it increases blood flow into the penis.

Follow your doctor’s dosing instructions, but generally, penile injections should not be used more than once in a 24-hour period, more than two days in a row, or more than two or three times in a week. To minimize side effects, advise your doctor of all other medications you are taking, especially ED medications. Taking oral ED medications with penile injections can increase the risk of side effects.

If an injection dose worked previously but fails now, check your technique to verify that you are injecting into the correct location and depth. Repeat dosing is risky. Especially when you are first using penile injections. Try to be patient as you find the best dosage for you and perfect your injection technique.

A Hand Writing Patience

What factors can affect how well penile injections work?

Penile injections contain medications that increase blood flow into the penis. If you have blood vessel disease or conditions that restrict blood flow into the penis, penile injections may not work for you.

What is the success rate of penile injections?

According to the American Urological Association, the success rate for penile injections ranges from 53.7% to 100% without marked differences across medication combinations. Satisfaction rates for penile injections as a treatment option for ED range from 46.3% to 98.8%. The lowest satisfaction rates were for papaverine.1  

How long can you use penile injections?

Penile injections can be used as long as necessary, as long as there are no contraindications to using them.

Contraindications for using penile injections include:

  • Having a hypersensitivity or allergy to any component of the compound
  • Having a medical condition that increases your risk of priapism, a painful erection that lasts longer than 4 hours
  • Having sickle cell, multiple myeloma, or leukemia
  • Having an anatomical deformity of the penis
  • Have an infection or sores on the penis

Tell your doctor about all medications you are taking and all current medical diagnoses. This will help them determine whether penile injections are safe for you.

Wegovy side effects

What are the potential side effects of penile injections?

All medications have side effects. When choosing the best ED treatment option, you and your doctor will weigh the risks and benefits and decide on an option that provides the most benefits at the lowest risks. Potential side effects from taking penile injections may include:

  • Priapism: this is one of the more serious potential side effects of using ED medications. A prolonged erection allows blood to sit in the penis for too long, decreasing oxygen levels and nutrients to sensitive penile tissues. Your doctor will discuss treatment options for priapism and provide guidance on when emergency treatment is necessary.
  • Bruising: bruising or swelling at the injection site may occur. You can reduce your risk of bruising by applying pressure to the injection site for 5 to 10 minutes.
  • Fibrosis or scarring: scarring of the penis may result in curvature or other penile deformities. To decrease your risk, do not inject more often than prescribed and alternate your injection sites. Some studies indicate that applying pressure to the injection site for 5 to 10 minutes may decrease your risk of scarring.

Other side effects associated with Trimix include:

  • Diarrhea
  • Nausea
  • Stomach cramps or vomiting
  • An allergic reaction
  • A sudden decrease in blood pressure
  • Increased heart rate or abnormal heart rhythm
  • Fainting
  • Dizziness

How long an erection lasts after a penile injection depends on several factors, including the following:

  • Current physical health
  • Comorbid medical conditions
  • Dosage
  • Degree of sexual stimulation
  • Other medication use
From Start to Finish: Understanding the Duration of a Penile Injection

How long do penile injections last?

Generally, erections develop within 10 to 15 minutes after a penile injection and last for about 30 minutes. Depending on your overall health, age, and medication doses, an erection may last longer.

Longer is not necessarily better. Aim for a dosage that results in sexual satisfaction, but not longer. If an erection lasts more than four hours, it can become very painful due to blood stasis and can cause damage to penile tissues.

Want to learn more about the benefits of penile injections? Contact one of the treatment specialists at Invigor Medical.

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From Start to Finish: Understanding the Duration of a Penile Injection
While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.

From Start to Finish: Understanding the Duration of a Penile Injection

Leann Poston, M.D.

Dr. Leann Poston is a licensed physician in the state of Ohio who holds an M.B.A. and an M. Ed. She is a full-time medical communications writer and educator who writes and researches for Invigor Medical. Dr. Poston lives in the Midwest with her family. She enjoys traveling and hiking. She is an avid technology aficionado and loves trying new things.


  • Burnett AL, Nehra A, Breau RH et al: Erectile dysfunction: AUA guideline. J Urol 2018; 200: 633.
  • Zelefsky MJ, Shasha D, Branco RD et al: Pro-phylactic sildenafil citrate improves select as-pects of sexual function in men treated with radiotherapy for prostate cancer. J Urol 2014;192:868


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