Injected Medicines for Erection Problems

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Injected Medicines for Erection Problems


Generic NameBrand Name
papaverine and phentolamineBimix
papaverine hydrochloride and phentolamine mesylate and alprostadilTrimix

The medicines in Bimix and Trimix must be mixed together by the pharmacist.

You inject this medicine into the side of the penis with a tiny needle.

See a picture of an injection.

Your doctor may give you a trial use of this medicine while you are in the office. This allows the doctor to see how well the medicine works for you, see whether you can use it properly, and check for adverse reactions, such as a painfully long-lasting erection (priapism) or an allergic reaction.

How It Works

The medicines are injected into the penis before sex to relax the muscles that surround the blood vessels in the penis, increasing the blood flow into the penis and producing an erection that lasts 30 minutes to an hour or longer. How long the erection lasts depends on how much medicine you inject.

Why It Is Used

These medicines may be prescribed for erection problems (erectile dysfunction) caused by psychological or physical factors.

How Well It Works

Papaverine by itself works in about half of the men who try it for erection problems. Alprostadil alone works in about 8 out of 10 men who try it for erection problems. The combination of papaverine and phentolamine (Bimix) works for about 7 out of 10 men who use it. Trimix (the combination of papaverine, phentolamine, and alprostadil) seems to work the best. It works in almost 9 out of 10 men who try it.1

Side Effects

Injections sometimes can result in a painful, prolonged erection (priapism). Call your doctor if an erection lasts longer than 3 hours. If the erection isn't relieved, it may damage tissues inside the penis.

Other side effects of injections may include:

  • Bruising.
  • Pain in the penis. Injecting the medicine slowly may help prevent pain.
  • Formation of scar tissue in the penis (fibrosis).

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

When thinking about injections for erection problems, it is important to include your partner in your decision.

These medicines are less likely to be effective for men in whom blood flow into or out of the penis is severely impaired.

They may cause problems for men with severe mental illness or for those who would have difficulty giving the injection. If you have vision problems, your partner can learn to give you the injections. Make sure your partner is comfortable with helping you and with using injections.

Medicines that are injected into the penis can be given no more than every other day. Excessive use may cause scarring.

Some men may find the idea of self-injections unpleasant, or they may find self-injections difficult to do. The use of an auto-injector, in which the needle is hidden, may make the shots easier for some men to use.

Couples trying to have children may prefer injections over a vacuum device, because the vacuum device blocks ejaculation.

Up to 60% of men stop using the medicines. Reasons include:2

  • Not wanting to use injections because of fear, discomfort, and the loss of spontaneity about giving an injection into the penis, or some other reason.
  • Partner relationship issues (being able to have erections doesn't solve relationship problems) or loss of partner.
  • Cost of the medicines.
  • Not being happy with the quality of erections from injections.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.



  1. Lue TF, Broderick GA (2007). Evaluation and nonsurgical management of erectile dysfunction and premature ejaculation. In AJ Wein, ed., Campbell-Walsh Urology, 9th ed., vol. 1, pp. 750–787. Philadelphia: Saunders Elsevier.
  2. Bella AJ, Lue TF (2008). Male sexual dysfunction. In EA Tanagho, JW McAninch, eds., Smith's General Urology, 17th ed., pp. 589–610. New York: McGraw-Hill.


By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Primary Medical Reviewer Andrew Swan, MD, CCFP, FCFP - Family Medicine
Specialist Medical Reviewer Christopher G. Wood, MD, FACS - Urology, Oncology
Last Revised July 13, 2010

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