Trimix injections for ED

Trimix is an injection of three drugs, alprostadil, papaverine and phentolamine, that a man injects into the side of the penis to get an erection, usually after ED pills haven’t worked. A compounding pharmacy prepares it for an individual prescription, and it isn’t FDA-approved. The FDA-approved injections for ED contain alprostadil alone and are sold as Caverject and Edex.

Studies at specialist clinics report that most men can have sex with it, but the injections need training, a prescriber who titrates the dose, and a plan for priapism, an erection that won’t go down. This guide covers what is in Trimix, what the studies found, the risks, how injecting works, what it costs and who prescribes it.

What is in Trimix

Each of the three drugs relaxes smooth muscle or widens blood vessels in a different way, and together they let blood fill the penis. Only one of them is approved for ED.

The Caverject label also speaks to mixtures directly: the safety and efficacy of combining it with other injected drugs “have not been systematically studied,” such combinations are “not recommended,” and the risks of prolonged erection, priapism and low blood pressure may be higher. Trimix is that kind of combination.

Does Trimix work?

The largest outcomes study is from Memorial Sloan Kettering Cancer Center in New York. It reviewed 1,412 men who started injection therapy between 2002 and 2006, most of them on Trimix, and 89% of Trimix users were able to have intercourse. Response was lower in men who had pelvic radiation or diabetes. Many men stopped within three years, and among men treated after prostate cancer surgery, many stopped because natural or pill-assisted erections came back.

A 2005 trial in Saudi Arabia randomized 180 men to one of nine Trimix dose combinations and gave each of them an alprostadil injection at a separate visit. Blood flow, rigidity, pain and satisfaction didn’t differ significantly between Trimix and alprostadil, but Trimix produced longer erections and more priapism.

For the approved product, Caverject’s label reports that over 80% of men in two of its trials had an erection good enough for intercourse, and in a 6-month home-use study of 683 men, 87% of 13,762 injections led to satisfactory sexual activity.

Risks: priapism first

An erection lasting more than 4 hours is a medical emergency. Caverject’s label says that if priapism isn’t treated quickly, penile tissue damage and permanent loss of potency can follow. Before your first home injection, ask your prescriber what to do and where to go if it happens.

The best-documented risk figures come from alprostadil alone, in Caverject’s trials of 1,861 men treated for up to 18 months:

• Penile pain: 37%, mostly mild or moderate; 3% stopped because of it.
• Prolonged erection (4 to 6 hours): 4%. Priapism (6 hours or more): 0.4%.
• Penile fibrosis (scarring): 3% overall, and 7.8% in an 18-month self-injection study.
• Bruising or bleeding at the site: hematoma 3%, ecchymosis 2%.

Trimix rates vary by study and dose. The New York review recorded priapism in 0.5%, and the 2005 trial found more priapism with Trimix than with alprostadil alone.

Caverject’s label says not to use it in men with conditions that raise the risk of priapism, such as sickle cell anemia or trait, multiple myeloma or leukemia, or for ED in men with penile scarring, curvature or Peyronie’s disease. Men on blood thinners may bleed more at the injection site. The AUA’s ejaculation guideline raises concern about priapism in men without ED who use injections to stay hard, and says injections don’t treat premature ejaculation.

There is a quality question too. The FDA says compounded drugs are not FDA-approved, so it does not verify their safety, effectiveness or quality before they are sold. Our guide to compounded and brand-name medications explains the difference.

Trimix, alprostadil or pills

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Injections don’t have to be permanent. In the New York review, many men treated after prostate cancer surgery stopped injecting once natural or pill-assisted erections returned.

Trimix: how to inject

Your prescriber sets the dose and teaches the technique, and only your prescriber should change the dose. Caverject’s label shows what supervised injection therapy looks like for the approved drug:

• The first injections are given in the clinician’s office, the dose is raised step by step to the lowest one that works, and you stay until the erection goes down.
• At home, you sit or recline, stretch the penis along the thigh, clean the site, and inject into the right or left side near the base, avoiding visible veins.
• You switch sides each time and press on the site for 5 minutes afterwards.
• Caverject is used no more than 3 times a week, at least 24 hours apart, with a check-up about every 3 months.

Ask whether your Trimix prescriber follows a similar plan, including an in-office test dose.

Trimix cost

We don’t list Trimix from any of the online providers we rank, even where one sells it, because we leave out compounded products that combine two or more drugs. For a published price, Defy Medical, a telehealth clinic we don’t list, estimated Trimix medication at $1.39 to $3.30 per injection, from the smallest dose to the largest, when we read its pages on Oct 27, 2026. It said a 5 mL vial lasts most patients two to three months and that its Trimix consult costs $75. Shipping, tax and injection supplies are extra, and Defy calls the figure an estimate, not a price guarantee.

For comparison, as of October 2026, generic sildenafil started at $25 a month at MyDrHank (it doesn’t state the strength or tablet count) and at $1.60 a 25 mg dose at Strut Health, with no needles. If you haven’t tried the approved pills at the right dose, start there; see the four FDA-approved ED pills or compare sildenafil providers.

Who prescribes Trimix

Urologists and men’s health clinics prescribe Trimix, and some telehealth clinics do after a consult; Defy Medical, for example, offers it by telemedicine to patients who qualify. The authors of the 2005 trial describe it as an option for men who don’t respond to alprostadil alone, find it painful, or find it too costly.

A good prescriber will review your heart health and medicines, start with a supervised test dose, explain how to store the vial, and give you a plan for an erection that lasts too long.

The bottom line

Trimix is a compounded mix of alprostadil, papaverine and phentolamine that works for most men in specialist programs, often when pills have failed. It isn’t FDA-approved, two of its three drugs aren’t approved for ED, and the approved alprostadil label says injected combinations are not recommended and may raise the risk of priapism and low blood pressure. Medication can cost a few dollars per injection. Use it only with a prescriber who supervises the first dose, and treat an erection over 4 hours as an emergency. Compare pill options in our ED provider rankings and on the ED hub.