Phenoxybenzamine

Phenoxybenzamine is a prescription medication used used to treat high blood pressure (hypertension) due to pheochromocytoma.

• Phenoxybenzamine is available under various brand names: Dibenzyline

Common side effects of Phenoxybenzamine include:

• stuffy nose,
• mild dizziness,
• drowsiness,
• blurred vision,
• trouble having an orgasm,
• upset stomach, and
• tiredness

Serious side effects of Phenoxybenzamine include:

• hives,
• difficulty breathing,
• swelling of the face, lips, tongue, or throat,
• severe dizziness, and
• lightheadedness

Rare side effects of Phenoxybenzamine include:

• none

Seek medical care or call 911 at once if you have the following serious side effects:

• Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
• Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
• Serious heart symptoms include fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheadedness, or passing out.

This is not a complete list of side effects and other serious side effects or health problems that may occur because of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

Adult and pediatric dosage

Capsule

• 10 mg

Hypertension Pheochromocytoma

Adult dosage

• 10 mg orally every 12 hours initially; increase every other day to 20-40 mg orally every 12 hours or every 8 hours (sometimes higher doses necessary)

Dosage Considerations – Should be Given as Follows: 

• See “Dosages”

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

• Phenoxybenzamine has severe interactions with no other drugs.
• Phenoxybenzamine has serious interactions with the following drugs:
  • lofexidine
  • sildenafil
  • tamsulosin
  • vardenafil
  • yohimbe
• Phenoxybenzamine has moderate interactions with at least 102 other drugs.
• Phenoxybenzamine has minor interactions with the following drugs:
  • brimonidine
  • butcher's broom
  • ethanol
  • phenylephrine
  • phenylephrine PO
  • tizanidine
  • treprostinil

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all your products. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your healthcare professional or doctor for additional medical advice, or if you have health questions or concerns.

Contraindications

• Hypersensitivity to phenoxybenzamine
• Any conditions in which a fall in BP is undesirable
• Orthostatic hypotension

Effects of drug abuse

• None

Short-Term Effects

• See “What Are Side Effects Associated with Using Phenoxybenzamine?”

Long-Term Effects

• See “What Are Side Effects Associated with Using Phenoxybenzamine?”

Cautions

• Cerebral or coronary arteriosclerosis, CHF, respiratory infection, renal impairment
• Concomitant use of drugs that stimulate alpha/beta receptors (may increase hypotension/tachycardia)
• May have carcinogenic potential
• Use caution in the elderly (increased risk of adverse effects)
• The first dose effect may occur, causing a sudden and drastic fall in blood pressure after administering the first dose.
• Hypotension/syncope may occur with the first few doses or with an increase in the dose
• Minimize by using a small first dose at bedtime
• Increase dose slowly

Pregnancy & Lactation

• Use with caution if benefits outweigh risks during pregnancy
• Lactation
  • Not known if excreted into breast milk, discontinue the drug or do not nurse