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Generic name: phenoxybenzamine [ fen-OX-ee-BENZ-a-meen ]
Brand name: Dibenzyline
Dosage form: oral capsule (10 mg)
Drug class: Miscellaneous cardiovascular agents

Medically reviewed by on Jun 3, 2024. Written by Cerner Multum.

What is phenoxybenzamine?

Phenoxybenzamine is used to control blood pressure and reduce sweating in people with pheochromocytoma (tumor of the adrenal gland).

Phenoxybenzamine may also be used for purposes not listed in this medication guide.

Phenoxybenzamine side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using phenoxybenzamine and call your doctor at once if you have severe dizziness or if you feel like you might pass out.

Common side effects of phenoxybenzamine may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Before taking this medicine

You should not use phenoxybenzamine if you are allergic to it.

Tell your doctor if you have ever had:

Tell your doctor if you are pregnant.

You should not breastfeed while using phenoxybenzamine.

How should I take phenoxybenzamine?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Call your doctor if you have fast heartbeats. You may need to be treated with an additional medication.

Store phenoxybenzamine at room temperature away from moisture and heat.

Phenoxybenzamine dosing information

Usual Adult Dose for Pheochromocytoma:

Initial dose: 10 mg orally twice daily
Maintenance dose: 20 to 40 mg orally 2 to 3 times daily until an optimal dosage (as judged by blood pressure control) is obtained.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include fast heart rate, vomiting, dizziness, or fainting.

What should I avoid while taking phenoxybenzamine?

Avoid driving or hazardous activity until you know how phenoxybenzamine will affect you. Your reactions could be impaired.

Avoid getting up too fast from a sitting or lying position, or you may feel dizzy.

Drinking alcohol with this medicine can cause side effects.

What other drugs will affect phenoxybenzamine?

Tell your doctor about all your other medicines, especially:

This list is not complete. Other drugs may affect phenoxybenzamine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.