Medically reviewed by Drugs.com. Last updated on Jan 4, 2022.
Commonly used brand name(s)
In the U.S.
Available Dosage Forms:
- Powder for Solution
Therapeutic Class: Antihypertensive
Pharmacologic Class: Alpha-Adrenergic Blocker
Uses for phentolamine
Phentolamine given by injection causes blood vessels to expand, thereby increasing blood flow. When injected into the penis (intracavernosal), it increases blood flow to the penis, which results in an erection.
Phentolamine should not be used as a sexual aid by men who do not have erectile dysfunction. If the medicine is not used properly, permanent damage to the penis and loss of the ability to have erections could result.
Phentolamine may also be used to reverse the effects of an anesthetic medicine in soft tissues, such as the lips and tongue. It may be used to help quickly restore normal sensation and function in patients who have received local dental anesthesia .
Phentolamine is available only with your doctor's prescription.
Before using phentolamine
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For phentolamine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to phentolamine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Appropriate studies have not been performed on the relationship of age to the effects of phentolamine for the reversal of soft-tissue anesthesia in children younger than 6 years of age. Safety and efficacy have not been established .
Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people. Although there is no specific information comparing the use of phentolamine for erectile dysfunction in the elderly, it is not expected to cause different side effects or problems in older people than it does in younger adults.
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking phentolamine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using phentolamine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Using phentolamine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Interactions with food/tobacco/alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Other medical problems
The presence of other medical problems may affect the use of phentolamine. Make sure you tell your doctor if you have any other medical problems, especially:
- Bleeding problems—These conditions increase the risk of bleeding at the place of injection.
- Priapism (history of) or
- Sickle cell disease—Patients with these conditions have an increased risk of priapism (erection lasting longer than 4 hours) while using phentolamine.
Proper use of phentolamine
To give the injection:
- Cleanse the injection site with alcohol. Using a sterile needle, inject the medicine slowly and directly into the base of the penis as instructed by your doctor. It should not be injected just under the skin. The injection is usually not painful, although you may feel some tingling in the tip of your penis. If the injection is very painful or you notice bruising or swelling at the place of injection, that means you are injecting the medicine under the skin. Stop, withdraw the needle, and reposition it properly before continuing with the injection.
- After you have completed the injection, put pressure on the place of injection to prevent bruising. Then massage your penis as instructed by your doctor. This helps the medicine spread to all parts of the penis, so that it will work better.
Phentolamine usually begins to work in about 10 minutes. You should attempt intercourse within 2 hours after injecting the medicine.
To reverse the effects of a soft-tissue anesthetic medicine, a dentist or other trained health professional will give you phentolamine. Phentolamine is usually injected at the same spot where you have received the local dental anesthesia .
The dose of phentolamine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of phentolamine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For injection dosage form:
- For the treatment of impotence:
- Adults— 0.5 to 1 milligram (mg) injected very slowly into the area of your penis as directed by your doctor. Allow one or two minutes to completely inject the dose. Do not inject more than one dose in a day. Also, do not use phentolamine more than two days in a row or more than three times a week.
- For the treatment of impotence:
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Precautions while using phentolamine
Use the injection exactly as directed by your doctor. Do not use more of it and do not use it more often than ordered. If too much is used, the erection may become so strong that it lasts too long and does not reverse when it should. This condition is called priapism, and it can be very dangerous. If the effect is not reversed, the blood supply to the penis may be cut off and permanent damage may occur.
Contact your doctor immediately if the erection lasts for longer than 4 hours or if it becomes painful. This may be a sign of priapism and must be treated right away to prevent permanent damage.
If you notice bleeding at the site when you inject the medicine, put pressure on the spot until the bleeding stops. If it doesn't stop, check with your doctor.
It is important for you to examine your penis regularly. Check with your doctor if you find a lump where the medicine has been injected or if you notice that your penis is becoming curved. These may be signs that unwanted tissue is growing (called fibrosis), which should be seen by your doctor.
Phentolamine side effects
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
- erection continuing for more than 4 hours, or painful erection
- lumps in the penis
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
Less common or rare
- Bruising or bleeding at place of injection
- burning (mild) along penis
- difficulty in ejaculating
- swelling at place of injection
Phentolamine injected into the penis may cause tingling at the tip of the penis. This is no cause for concern.
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
More about phentolamine
- Side effects
- Drug interactions
- Dosage information
- During pregnancy
- Pricing & coupons
- Drug class: miscellaneous cardiovascular agents
Related treatment guides
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.