Phenoxybenzamine: Uses, Dosage, Side Effects and More

Generic Medicine Info Patient Medicine Information

This information is not country-specific. Please refer to the Malaysia prescribing information.

Generic Medicine Info

Indications and Dosage

Oral
Hypertension in phaeochromocytoma

Adult: Initially, 10 mg daily; may increase gradually based on patient's response. Usual dosing range: 1-2 mg/kg daily in 2 divided doses.
Child: There is limited information regarding the use of this drug in this population, dosage and treatment recommendations may vary among countries and between individual products (refer to specific product guidelines).

Contraindications

Cerebrovascular accident; during recovery period (usually 3-4 weeks) after acute MI; conditions where a decrease in blood pressure is undesirable.

Special Precautions

Patient with severe heart disease, CHF, cerebrovascular disease, respiratory infections. Concomitant administration with agents that stimulate α- and β-adrenergic receptors. Renal impairment. Children and elderly. Pregnancy and lactation.

Adverse Reactions

Eye disorders: Miosis.
Gastrointestinal disorders: Gastrointestinal upset.
General disorders and administration site conditions: Lassitude.
Nervous system disorders: Dizziness.
Reproductive system and breast disorders: Inhibition of ejaculation.
Respiratory, thoracic and mediastinal disorders: Nasal congestion.

Monitoring Parameters

Monitor orthostatics, blood pressure and pulse.

Overdosage

Symptoms: Profound hypotension. Management: Symptomatic and supportive treatment. Perform gastric lavage and induce emesis. Administer plasma expanders for hypotension.

Drug Interactions

Increased risk of exaggerated hypotensive response and tachycardia with agents that stimulate both α- and β-adrenergic receptors (e.g. epinephrine).

Action

Description:
Mechanism of Action: Phenoxybenzamine is a long-acting α-adrenergic receptor blocker. It binds covalently to α-receptors in the smooth muscles, resulting in an irreversible or non-competitive blockade of postgalglionic synapses. Additionally, it relaxes the urethra and increases the bladder opening.
Onset: Within 2 hours.
Duration: 3-4 days.
Pharmacokinetics:
Absorption: Incompletely absorbed from the gastrointestinal tract. Bioavailability: 20-30%.
Distribution: Distributes into and may accumulate in adipose tissues.
Metabolism: Metabolised in the liver.
Excretion: Mainly via urine and bile. Elimination half-life: Approx 24 hours.

Chemical Structure

Storage

Store between 15-30°C. Protect from light.

MIMS Class

Other Antihypertensives

ATC Classification

C04AX02 - phenoxybenzamine ; Belongs to the class of other peripheral vasodilators.

References

Anon. Phenoxybenzamine Hydrochloride. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 08/11/2024.

Brayfield A, Cadart C (eds). Phenoxybenzamine Hydrochloride. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 08/11/2024.

Dibenyline 10 mg Capsules (Mercury Pharmaceuticals Ltd). MHRA. https://products.mhra.gov.uk. Accessed 08/11/2024.

Dibenzyline Capsule (Concordia Pharmaceuticals Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 08/11/2024.

Joint Formulary Committee. Phenoxybenzamine Hydrochloride. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 08/11/2024.

Paediatric Formulary Committee. Phenoxybenzamine Hydrochloride. BNF for Children [online]. London. BMJ Group, Pharmaceutical Press, and RCPCH Publications. https://www.medicinescomplete.com. Accessed 21/01/2025.

Phenoxybenzamine. UpToDate Lexidrug, Lexi-Drugs Multinational Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 02/12/2024.

Disclaimer: This information is independently developed by MIMS based on Phenoxybenzamine from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2025 MIMS. All rights reserved. Powered by MIMS.com