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Phenoxybenzamine is used in the treatment of high blood pressure caused due to a tumor of the adrenal glands (Phaeochromocytoma). Adrenal glands are small glands located on top of each kidney.

How it works

Phenoxybenzamine belongs to a class of drugs called alpha blockers. It acts on nerve endings of the blood vessels which causes muscle relaxation, thereby lowering blood pressure.

Common side effects

Dizziness, Fainting, Nasal congestion, Sexual dysfunction, Tachycardia, Vomiting, Stomach upset


Expert advice

  • Exercise caution during treatment with phenoxybenzamine in an elderly patient.
  • Inform your doctor, if you have any heart complaints, brain arteries thickening, low blood pressure or kidney diseases.
  • Do not drive or operate machinery as phenoxybenzamine may cause drowsiness or dizziness.
  • Tell your doctor if you are pregnant or planning to become pregnant or are breastfeeding.

Frequently asked questions


Q. How long and quick does phenoxybenzamine take to work?
The effect of phenoxybenzamine starts in about 1 hour after an intravenous dose. Following oral administration, the action starts gradually over several hours and persists for 3-4 days following a single dose.
Q. Is phenoxybenzamine an antibiotic?
No, phenoxybenzamine is not used as an antibiotic.

Content on this page was last updated on 03 October, 2016, by Dr. Varun Gupta (MD Pharmacology)