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Overview: Phenoxybenzamine is commonly used to treat high blood pressure or to treat excess sweating in certain people. It works by relaxing blood vessels and by blocking the effect of certain nerve signals throughout the body. Common side effects may include fast heartbeat, dizziness, stomach upset, and drowsiness. Because phenoxybenzamine may cause dizziness or drowsiness, do not drive or do other activities that require coordination until you know how this medicine affects you. Phenoxybenzamine is a capsule that is taken by mouth. 

Uses

What is phenoxybenzamine used for?

Phenoxybenzamine is commonly used to treat high blood pressure and excess sweating in people with a rare type of tumor called pheochromocytoma.

Phenoxybenzamine may also be used for other conditions as determined by your health care provider.

How does phenoxybenzamine work (mechanism of action)?

Phenoxybenzamine is an alpha blocker. It works to relax and widen the blood vessels throughout your body. This lets blood move through the vessels more easily, which lowers blood pressure. 

Phenoxybenzamine also reduces sweating. It blocks the effect of certain nerve signals throughout your body, including your sweat glands.

How is phenoxybenzamine supplied (dosage forms)?

Brands and other names

  • Dibenzyline

Dosage forms and strengths

  • 10 mg oral capsules

How should I store phenoxybenzamine?

Phenoxybenzamine should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Side Effects

What are the most common side effects of phenoxybenzamine?

The most common side effects of phenoxybenzamine are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Fast heartbeat
  • Dizziness
  • Less semen than unusual (retrograde ejaculation)
  • Stuffy nose
  • Small pupils
  • Stomach upset
  • Drowsiness
  • Tiredness

There may be other side effects of phenoxybenzamine that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of phenoxybenzamine?

While less common, the most serious side effects of phenoxybenzamine are described below, along with what to do if they happen.

Severe Allergic Reactions. Phenoxybenzamine may cause allergic reactions, which can be serious. Stop taking phenoxybenzamine and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Low Blood Pressure Upon Standing (Orthostatic Hypotension). Phenoxybenzamine may cause a sudden drop in blood pressure when standing up from a seated or lying position. To help prevent this, be careful not to get up too quickly. If you feel dizzy, sit or lie down right away until the dizziness stops, then take your time getting up again. Tell your health care provider right away if you have any of the following symptoms of orthostatic hypotension.

  • Dizziness, feeling lightheaded, or fainting upon standing
  • Blurred vision
  • Confusion
  • Feeling weak
  • Feeling like your heart is racing or skipping (palpitations)

Warnings & Precautions

Who should not use phenoxybenzamine?

Allergies to Ingredients. People who are allergic to any of the following should not take phenoxybenzamine.

  • Dibenzyline
  • Phenoxybenzamine
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific phenoxybenzamine products they stock.

Low Blood Pressure. Phenoxybenzamine can cause a drop in blood pressure. You should not take phenoxybenzamine if you have a condition that gets worse when your blood pressure is lowered. Tell your health care provider about any health conditions you have. This can help them decide if this medicine is safe for you.

What should I know about phenoxybenzamine before taking it?

Do not take phenoxybenzamine unless it has been prescribed to you by a health care provider. Take it as prescribed.

Do not share phenoxybenzamine with other people, even if they have the same condition as you. It may harm them.

Keep phenoxybenzamine out of the reach of children.

Phenoxybenzamine may cause dizziness and drowsiness. Do not drive or do other activities that require alertness and coordination until you know how this medicine affects you.

What should I tell my health care provider before taking phenoxybenzamine?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if phenoxybenzamine is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

Other Medicines and Supplements. Phenoxybenzamine may interact with other medicines and supplements. Before taking phenoxybenzamine, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how phenoxybenzamine could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if phenoxybenzamine passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does phenoxybenzamine interact with foods or drinks?

There are no known interactions between phenoxybenzamine and foods or drinks.

It is unknown if drinking alcohol will affect phenoxybenzamine. The risk of side effects, such as dizziness, may be higher if you drink alcohol while taking phenoxybenzamine.

Does phenoxybenzamine interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking phenoxybenzamine. 

  • A medicine for high blood pressure
  • Epinephrine (Adrenaclick, Auvi-Q, Epipen, and others), a medicine used for severe allergic reactions and other conditions
  • Norepinephrine (Levophed), also called levarterenol, a medicine used in an emergency for low blood pressure, heart attack, and other conditions

This may not be a complete list of medicines that can interact with phenoxybenzamine. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much phenoxybenzamine?

If you or someone else has used too much phenoxybenzamine, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of phenoxybenzamine?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses. 

Images

Dibenzyline

GENERIC: Phenoxybenzamine

Imprint: 10 MG WPC 001
Strength: 10 mg
Color: red
Shape: oblong