Phenoxybenzamine

Mechanism-of-action class: Adrenergic alpha-Antagonists.

• INDICATION AND USAGE Phenoxybenzamine hydrochloride capsules are indicated in the treatment of pheochromocytoma, to control episodes of hypertension and sweating. If tachycardia is excessive, it may be necessary to use a beta -blocking agent concomitantly.ICD-10: I10

• Conditions where a fall in blood pressure may be undesirable; hypersensitivity to the phenoxybenzamine hydrochloride capsules, or any of its components.contraindicated

The dosage should be adjusted to fit the needs of each patient. Small initial doses should be slowly increased until the desired effect is obtained or the side effects from blockade become troublesome. After each increase, the patient should be observed on that level before instituting another increase . The dosage should be carried to a point where symptomatic relief and/or objective improvement are obtained, but not so high that the side effects from blockade become troublesome. Initially, 10 mg of phenoxybenzamine hydrochloride twice a day. Dosage should be increased every other day, usually to 20 mg to 40 mg 2 or 3 times a day, until an optimal dosage is obtained, as judged by blood pressure control. Long-term use of phenoxybenzamine is not recommended (see PRECAUTIONS - Carcinogenesis and Mutagenesis ).

Phenoxybenzamine hydrochloride-induced alpha -adrenergic blockade leaves beta -adrenergic receptors unopposed. Compounds that stimulate both types of receptors may, therefore, produce an exaggerated hypotensive response and tachycardia.

The following adverse reactions have been observed, but there are insufficient data to support an estimate of their frequency. Autonomic Nervous System*: Postural hypotension, tachycardia, inhibition of ejaculation, nasal congestion, miosis. *These so-called “side effects” are actually evidence of adrenergic blockade and vary according to the degree of blockade. Miscellaneous: Gastrointestinal irritation, drowsiness, fatigue. To report SUSPECTED ADVERSE REACTIONS, contact Amneal Pharmaceuticals at 1-877-835-5472 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Pregnancy - Teratogenic Effects Adequate reproductive studies in animals have not been performed with phenoxybenzamine hydrochloride. It is also not known whether phenoxybenzamine hydrochloride can cause fetal harm when administered to a pregnant woman. Phenoxybenzamine hydrochloride should be given to a pregnant woman only if clearly needed.

SYMPTOMS - These are largely the result of blocking of the sympathetic nervous system and of the circulating epinephrine. They may include postural hypotension, resulting in dizziness or fainting; tachycardia, particularly postural; vomiting; lethargy; shock. Treatment When symptoms and signs of overdosage exist, discontinue phenoxybenzamine hydrochloride capsules. Treatment of circulatory failure, if present, is a prime consideration. In cases of mild overdosage, recumbent position with legs elevated usually restores cerebral circulation. In the more severe cases, the usual measures to combat shock should be instituted. Usual pressor agents are not effective. Epinephrine is contraindicated because it stimulates both alpha - and beta - receptors; since alpha- receptors are blocked, the net effect of epinephrine administration is vasodilation and a further drop in blood pressure (epinephrine reversal). The patient may have to be kept flat for 24 hours or more in the case of overdose, as the effect of the drug is prolonged. Leg bandages and an abdominal binder may shorten the period of disability.

• Oct 27, 2020ANDAANDA212568Amneal
• Jul 19, 2022ANDAANDA215042Novitium Pharma
• May 8, 2023ANDAANDA215600Aurobindo Pharma

1. 1Urinary Tract Infection623%
2. 2Covid-19415%
3. 3Blood Pressure Decreased312%
4. 4Diarrhoea312%
5. 5Dizziness312%
6. 6Headache312%
7. 7Influenza312%
8. 8Catastrophic Reaction27.7%
9. 9Constipation27.7%
10. 10Cystitis27.7%
11. 11Dehydration27.7%
12. 12Delirium27.7%
13. 13Device Use Issue27.7%
14. 14Fatigue27.7%
15. 15Feeding Disorder27.7%

Recent PubMed references pinned to Phenoxybenzamine as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

• Management of refractory hypotension during adrenalectomy in a dog treated with phenoxybenzamine.
  Veterinary anaesthesia and analgesia · 2025 · Machado ML, Pypendop BH, Soares JH, et al.
  PMID 40189441DOI 10.1016/j.vaa.2025.03.005
• Short-acting urapidil compared to long-acting phenoxybenzamine in the management of pheochromocytoma.
  Langenbeck's archives of surgery · 2025 · Feld A, Mintziras I, Wächter S, et al.
  PMID 39934496DOI 10.1007/s00423-025-03627-6
• Retrospective evaluation of the influence of phenoxybenzamine pretreatment on intraoperative cardiovascular variables in dogs with pheochromocytoma.
  The Canadian veterinary journal = La revue veterinaire canadienne · 2024 · Willette C, Bini G, Traverson M, et al.
  PMID 39649740
• 52-Year-Old Woman With Fever, Diaphoresis, and Abdominal Pain.
  Mayo Clinic proceedings · 2020 · Breen TJ, Ingraham BS, Jentzer JC, et al.
  PMID 32622460DOI 10.1016/j.mayocp.2019.11.032
• The Duration of Preoperative Administration of Single α-Receptor Blocker Phenoxybenzamine before Adrenalectomy for Pheochromocytoma: 18 Years of Clinical Experience from Nationwide High-Volume Center.
  BioMed research international · 2019 · Tian J, Bao Z, Yuan Y, et al.
  PMID 31828097DOI 10.1155/2019/2613137
• Discovery of novel phenoxybenzamide analogues as Raf/HDAC dual inhibitors.
  Bioorganic & medicinal chemistry letters · 2019 · Geng A, Cui H, Zhang L, et al.
  PMID 31053508DOI 10.1016/j.bmcl.2019.04.047
• Anti-tumor activity of phenoxybenzamine and its inhibition of histone deacetylases.
  PloS one · 2018 · Inchiosa MA Jr
  PMID 29897996DOI 10.1371/journal.pone.0198514
• Giant malignant pheochromocytoma in an elderly patient: A case report.
  Medicine · 2018 · Ma C, Sun E, Lu B, et al.
  PMID 29742697DOI 10.1097/MD.0000000000010614

The 9 most recently updated of 9 ClinicalTrials.gov registrations naming Phenoxybenzamine as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

• Post-mastectomy Recovery: Comparing Preoperative PECS-II Blocks With Intraoperative Pectoral Blocks
  Recruiting · Phase 4 · Interventional · 100 enrolled · University of Cincinnati
  NCT06574022updated 2025-11-04
• The Effect and Safety of Omitting Preoperative Alpha-adrenergic Blockade for Normotensive Pheochromocytoma
  Recruiting · Phase 4 · Interventional · 24 enrolled · Seoul National University Hospital
  NCT05702944updated 2025-06-12
• Phenoxybenzamine Versus Doxazosin in PCC Patients
  Completed · Phase 4 · Interventional · 134 enrolled · University Medical Center Groningen
  NCT01379898updated 2024-09-19
• Preoperative Alpha Blockade for Pheochromocytoma
  Completed · Phase 3 · Interventional · 39 enrolled · University of California, Los Angeles
  NCT03176693updated 2023-11-20
• Selective Versus Nonselective Alpha-blockade Prior to Pheochromocytoma Resection - Systematic Review and Meta-analysis
  Completed · Observational · 1,344 enrolled · Jagiellonian University
  NCT04557072updated 2021-06-18
• Pheochromocytoma and Hemodynamic Instability
  Completed · Observational · 96 enrolled · Jagiellonian University
  NCT04566406updated 2020-09-28
• Use of Phenoxybenzamine [PBZ] IV to Assist High Flow Low Pressure Perfusion [HFLPP] on Cardio-pulmonary Bypass
  Terminated · Interventional · 87 enrolled · The Cleveland Clinic
  NCT00620945updated 2017-12-19
• Parenteral Phenoxybenzamine During Congenital Heart Disease Surgery
  Withdrawn · Phase 2 · Interventional · 0 enrolled · Vanderbilt University
  NCT00770705updated 2017-05-01
• Intravenous Phenoxybenzamine Use in Pediatric Patients Undergoing Open-Heart Surgery
  Completed · Phase 2 · Interventional · 785 enrolled · University of Arkansas
  NCT00569855updated 2011-03-01

Frequently asked questions

How does Phenoxybenzamine work?

Mechanism-of-action class: Adrenergic alpha-Antagonists.

What is Phenoxybenzamine used for?

According to FDA labeling, Phenoxybenzamine carries indications including: INDICATION AND USAGE Phenoxybenzamine hydrochloride capsules are indicated in the treatment of pheochromocytoma, to control episodes of hypertension and sweating. If tachycardia is excessive, it may be necessary to use a beta -blocking agent concomitantly.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.

What class of drug is Phenoxybenzamine?

Phenoxybenzamine is classified as Other peripheral vasodilators, alpha-Adrenergic Blocker, Adrenergic alpha-Antagonists, Decreased Bladder Sphincter Tone, Decreased Blood Pressure, Decreased Urethra Smooth Muscle Tone.

What are the brand names for Phenoxybenzamine?

Phenoxybenzamine is marketed under brand names including Dibenzyline.

What are the contraindications for Phenoxybenzamine?

Phenoxybenzamine labeling lists contraindications including: Conditions where a fall in blood pressure may be undesirable; hypersensitivity to the phenoxybenzamine hydrochloride capsules, or any of its components.. Always consult the full prescribing information and a clinician.