Health Guide

Phentolamine (By injection)

Phentolamine (fen-TOL-a-meen)

Prevents and controls high blood pressure during surgery. Prevents and treats skin injury caused by norepinephrine injection. Used during a medical procedure to diagnose pheochromocytoma (an adrenal gland tumor).

Brand Name(s):

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. You should not receive it if you had an allergic reaction to phentolamine, or if you have low blood pressure, heart disease, angina (chest pain), or a history of heart attack.

How to Use This Medicine:


  • This medicine is given through a needle placed in one of your veins or as a shot into your muscle. This medicine may also be injected in your mouth after a dental procedure.
  • A dentist, nurse, or other trained health professional will give you this medicine.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Some medicines can affect how phentolamine works. Tell your doctor if you are using any of the following:
    • Guanethidine
    • Reserpine
    • Digitalis
    • Insulin
    • Antidepressants
    • Blood pressure medicine
  • Tell your doctor if you use anything else that makes you sleepy. Some examples are allergy medicine, narcotic pain medicine, and alcohol.

Warnings While Using This Medicine:

  • Tell your doctor if you are pregnant or breastfeeding, or if you have heart rhythm problems, kidney disease, a sulfite sensitivity, gastritis, or a peptic ulcer.
  • This medicine may make you dizzy or drowsy. Do not drive, use machines, or do anything that could be dangerous until you know how this medicine affects you.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Chest pain that may spread to your arms, jaw, back, or neck, trouble breathing, nausea, unusual sweating
  • Fast or uneven heartbeat
  • Lightheadedness or fainting
  • Numbness or weakness in your arm or leg, or on one side of your body
  • Sudden or severe headache, problems with vision, speech, or walking

If you notice these less serious side effects, talk with your doctor:

  • Nausea, vomiting, or diarrhea
  • Stuffy nose
  • Warmth or redness in your face, neck, arms, or upper chest

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 7/4/2018
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