Phentolamine Injections for Erectile Dysfunction

Until Viagra became available in 1998, the most effective medication for the treatment of erectile dysfunction, or ED, was a procedure known as injection therapy. Various medications have been used in this type of therapy, but phentolamine is widely regarded to be among the most effective. As suggested by the name, injection therapy involves injecting chemicals into the penis to achieve and sustain an erection that lasts long enough to successfully engage in sexual intercourse. Phentolamine is typically injected alone, but it is occasionally injected along with other medications to ensure optimal results.

What is Phentolamine?

Phentolamine is what is known as a smooth muscle relaxant. When used for the treatment of erectile dysfunction, it is designed to be injected directly into the penis. For this reason, many men are reluctant to use it as they are anxious about injecting medication into such a sensitive part of the body. However, phentolamine injections are very dependable and work for the vast majority of men with ED. It is effective for ED stemming from nearly all known causes, including psychological and physical ones, so it is a viable option for men who have tried other medications and therapies with little or no success.

The generic name for this medication is phentolamine. It is marketed and prescribed under a variety of brand names, with OraVerse and Regitine being the most ubiquitous.

How Phentolamine Injections Work

Phentolamine is a smooth muscle relaxant. When used to treat erectile dysfunction, it works by causing blood vessels in the penis to expand, which increases blood flow and ultimately causes an erection.

More specifically, phentolamine and similar medications work by blocking the nerves that signal arterial walls to contract. Arterial contraction constricts blood flow. Without adequate blood flow to the penis, an erection is not possible. When phentolamine is injected into a corpora cavernosa of the penis — there are two of such tube-shaped structures — the muscle cells in the arterial walls relax, and the arteries dilate. In turn, blood can flow freely into the corpora cavernosa. At the same time, veins should remain constricted, which helps to keep the blood there long enough for an erection to occur.

When an erection is achieved using a phentolamine injection, a man is still able to achieve orgasm as usual. Of course, men who have difficulty achieving orgasm or who are unable to completely will still experience these issues despite the use of phentolamine. Similarly, ejaculation can still occur as usual when phentolamine injections are used, which is why this type of therapy may be recommended for couples who are trying to conceive.

Other Uses

Like many prescription medications, phentolamine is used to treat several conditions. While it is best known for use in injection therapies for erectile dysfunction, it is also used in dental offices to counteract the effects of local anesthetics like Novocaine. It only reverses the effect of local anesthetics in soft tissues like the tongue and lips. If too much anesthetic is used, or if a patient needs the numbness to subside more quickly for some reason, a dentist may inject phentolamine at the site to achieve this.

Phentolamine may also be used as an anti-hypertensive before surgery. Just before undergoing surgery, some patients experience high blood pressure due to anxiety. This may adversely affect the anesthetics being used or the procedure itself, and phentolamine can counteract these symptoms to ensure a less cumbersome operation.


Men who experience certain medical conditions should not use phentolamine or should take extra caution when doing so. Fortunately, however, phentolamine is generally safe for nearly everyone.

Men who have bleeding problems should use caution when using phentolamine injection therapy for erectile dysfunction. They are more likely to experience bleeding at the injection site. While a small amount of bleeding is usually no cause for concern, it may indicate a larger problem if it is excessive or doesn’t stop within a few minutes.

Men with a history of priapism, which is a condition in which erections last far longer than normal and may even be painful, are not ideal candidates for phentolamine injections. That is mostly because priapism is a rare side effect of such injections.

Finally, men who suffer from sickle cell disease are advised not to use phentolamine. Sickle cell disease increases a man’s risk of priapism. Even sickle cell sufferers with no prior history of priapism should generally avoid using phentolamine.

Drug Interactions

It is generally not recommended to use phentolamine in combination with tadalafil. However, in certain cases, a doctor may allow a patient to do so.

Caution should be used before using phentolamine in combination with any of the following medications. As with tadalafil, however, it is sometimes necessary for men to use both simultaneously. In that case, more careful supervision may be required to ensure safety. These medications may increase the risk of phentolamine’s most common side effects:

• Acebutolol

• Alprenolol

• Atenolol

• Betaxolol

• Bevantolol

• Bisoprolol

• Bucindolol

• Carteolol

• Carvedilol

• Celiprolol

• Dilevalol

• Esmolol

• Labetalol

• Levobunolol

• Mepindolol

• Metipranolol

• Metoprolol

• Nadolol

• Nebivolol

• Oxprenolol

• Penbutolol

• Pindolol

• Propranolol

• Sotalol

• Talinolol

• Tertatolol

• Timolol

• Vardenafil

Side Effects of Phentolamine Injections

When using phentolamine injections, men should contact their doctors immediately if they notice certain rare but potentially serious side effects, including dizziness, lumps in the penis, or erections that are painful or that last for more than four hours.

Less common side effects that may occur when using phentolamine include difficult ejaculation, swelling at the injection site, bruising and/or bleeding at the injection site, and a mild burning sensation along the penis. Patients are advised to ask their doctors about such side effects should they occur. Many times, they subside as the body acclimates to phentolamine injections.

How Phentolamine Injections are Prescribed

Phentolamine injections are available by prescription only. In most cases, doctors administer the first dose to patients before sending them home with the medication. Many men have never given injections at all, so they must be taught how to do so safely and effectively. Also, because priapism occurs in about 2 percent of cases, doctors perform the first injection at the office to keep an eye on the patient. Priapism is most likely to occur during the first use. If a doctor notices the signs of priapism, he can administer another drug that reverses the effects of phentolamine.

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When used to treat erectile dysfunction, phentolamine is typically administered in doses of 0.5 to 1 milligram per injection. The exact dose will vary depending on a few factors. Patients are advised to follow the doctor’s orders or to refer to the label on their medication. The amount of the dose depends on the strength of the phentolamine that is being used. Also, the nature of the erectile dysfunction that is being treated will affect the allowed number of daily doses, the time allowed between doses, and the length of time during which injections may be given.

How to Use Phentolamine Injections

Most men are understandably anxious about using phentolamine injections for the first time. Men who are physically unable to inject themselves may have a partner do it for them. For instance, men who have vision problems or men who are obese and cannot easily see the penis may require assistance.

When injecting phentolamine, a clean, sterile needle must be used every time, or infection may occur.

Although phentolamine is typically injected with a standard, small needle, an auto-injector, in which the needle is hidden, may be used for patients who are extremely anxious about injecting themselves with the medication.

Before injecting phentolamine, the injection site should be thoroughly cleaned with alcohol. The injection is not to be administered just under the skin; it must reach the corpora cavernosa. Patients are typically instructed to inject the medication into the base of the penis. The injection must be administered slowly, for a minute or two.

Phentolamine injections are not generally painful. However, they may produce a slight tingling sensation in the penis. If an injection is painful, or if it produces swelling or bruising at the injection site, it is only going just under the skin and should be attempted again.

Immediately after the injection is complete, a patient should put pressure on the injection site to help ward off bruising. Next, the penis should be massaged as directed by the doctor to help spread the medication more effectively.

Phentolamine injections typically start working within about 10 minutes. Patients should engage in sexual intercourse within two hours of administering their injections.

Precautions to Take When Using Phentolamine Injections

Patients should take care not to use too much phentolamine or to use it more often than recommended. If too much of the medication is injected, the resulting erection may be too strong, or it may last too long. This could lead to priapism, which is a potentially dangerous condition in which blood supply to the penis is cut off and permanent damage may occur.

The following points should be kept in mind when using phentolamine:

• If an erection becomes painful or lasts for more than four hours, contact a doctor.

• If bleeding occurs at the injection site, apply pressure. If the bleeding continues despite applying pressure, seek medical attention.

• If a lump appears at the injection site, or if the penis starts taking on a curved shape over time, unwanted tissue may be building up in the area. This is known as fibrosis, and it requires medical attention. Men who are using phentolamine injection therapy are advised to inspect their penises regularly.

A Brief History of Injection Therapy for Erectile Dysfunction

Injection therapy was the first FDA-approved medication for the treatment of erectile dysfunction, and phentolamine has long been the medication of choice for such therapy. It continues to be the only medication that will initiate an erection. Drugs like Viagra still require sexual stimulation for an erection to be initiated.

While performing bypass surgery in 1977, a surgeon accidentally injected a drug called papaverine near the impotent patient’s penis. This resulted in a long, completely rigid erection that lasted for two hours. From this, subsequent research using a variety of different chemicals and medications was performed. It was discovered that phentolamine caused erections in cats. In 1982, a French doctor noted that papaverine increased pressure in the penis, resulting in reliable erections. The following year, a London doctor engaged in a study involving 11 impotent men. Upon receiving injection therapy, the patients were able to have satisfactory intercourse.


The success rate of phentolamine injections ranges from 70 percent to 94 percent. It is effective in treating erectile dysfunction arising from all causes. This is important because ED can be triggered by a vast array of conditions, including psychological and physical issues. Because it has no negative impact on orgasm or ejaculation, phentolamine is widely considered to be one of the best treatments for ED. Despite that, however, it has never achieved the prominence of drugs like Viagra, which are administered orally rather than being injected. Squeamishness about injecting chemicals into the penis has put a damper on the popularity of phentolamine, but it continues to be prescribed for many patients.


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