Phenoxybenzamine
Phenoxybenzamine is an alpha-blocker used to control high blood pressure and sweating caused by pheochromocytoma, a tumor of the adrenal gland.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 6 clinical label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
Phenoxybenzamine (Dibenzyline) is a specialist alpha-blocker, on the market since the 1950s and available as a generic, that controls the dangerous blood pressure spikes and sweating of pheochromocytoma (a rare adrenal gland tumor) by blocking the receptors stress hormones use to tighten blood vessels, so the vessels relax. Its side effects are expected rather than rare, most often dizziness when standing, a stuffy nose and a faster heartbeat, which is why the dose starts low and rises gradually. The one thing to watch for is epinephrine (adrenaline), including an EpiPen, because with alpha receptors blocked it can drop blood pressure further and make the heart race.
Clinical pearls
- Long-term use is not recommended because of cancer concerns in lab studies, so know your planned stopping point from the start.
- Tell every dentist, surgeon and emergency team you take it, since some numbing injections contain epinephrine.
- Stand up slowly, especially in the days after a dose increase, because fainting means your blood pressure is dropping too far.
- A heart that keeps racing is worth reporting, because the label allows a beta-blocker to be added alongside to slow it.
Patient information guide A plain-language walkthrough of Phenoxybenzamine, written from its FDA label.
What Phenoxybenzamine is used for
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Phenoxybenzamine hydrochloride capsules are approved for one specific condition:
- Pheochromocytoma: Phenoxybenzamine hydrochloride capsules are used to control episodes of high blood pressure and excessive sweating caused by this rare adrenal gland tumor. If the heart rate also becomes too fast, a beta-blocking drug may be added by the prescriber.
How Phenoxybenzamine works
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Phenoxybenzamine works by permanently blocking alpha-adrenergic receptors — the sites on blood vessel walls that stress hormones (like adrenaline) normally attach to in order to narrow vessels and drive blood pressure up. By locking those receptors out, phenoxybenzamine widens blood vessels, improves blood flow to the skin, mucous membranes, and abdominal organs, and lowers blood pressure whether you're lying down or standing up. It does not affect the parasympathetic (rest-and-digest) nervous system.
Because it only blocks alpha receptors and leaves beta receptors untouched, drugs that stimulate both receptor types — like epinephrine — can cause an outsized drop in blood pressure. This is an important interaction to understand.
Phenoxybenzamine dosage
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Phenoxybenzamine hydrochloride is taken by mouth as a capsule, usually starting twice a day at a low dose. The dose is increased gradually every other day until blood pressure is well controlled or side effects become a limiting factor. Your prescriber will find the right level for you — the goal is symptom relief without troublesome side effects.
- Take as directed; do not adjust the dose on your own
- Long-term use is not recommended — talk to your doctor about your treatment plan and duration
Dosing details from the FDA-approved label
From the Phenoxybenzamine prescribing information (“Dosage and Administration”). Doses are set by your prescriber for your product, condition, kidney function and age — never change a dose on your own.
- Phenoxybenzamine hydrochloride therapy (blood pressure control)
- Initially, 10 mg of phenoxybenzamine hydrochloride twice a day
- Dosage should be increased every other day, usually to 20 to 40 mg 2 or 3 times a day, until an optimal dosage is obtained, as judged by blood pressure control
- Adjust to each patient's needs; increase slowly and observe the patient at each level; long-term use is not recommended
Read the label’s full dosing text
DOSAGE AND ADMINISTRATION 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 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 ). STORAGE Store at 20° to 25°C (68° to 77°F); excursions permitted to 15° to 30°C (59° to 86°F) [See USP Controlled Room Temperature]. Dispense in a tight container.
Read the full Dosage and Administration section on DailyMed →
Phenoxybenzamine side effects
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Because phenoxybenzamine works by blocking the sympathetic (fight-or-flight) nervous system, many of its side effects are direct results of that blockade — not unexpected reactions:
Common side effects
- Dizziness or light-headedness when standing up (postural hypotension)
- Fast heart rate (tachycardia)
- Stuffy nose (nasal congestion)
- Smaller than usual pupils (miosis)
- Difficulty or inability to ejaculate
- Upset stomach or gastrointestinal irritation
- Drowsiness
- Fatigue
- Inhibition of ejaculation
When to get medical help
- Call your doctor if you faint or feel severely dizzy, especially when standing — this may signal a dangerous drop in blood pressure.
- Seek medical help right away if you experience shock-like symptoms: cold, clammy skin, rapid weak pulse, or confusion.
- Tell your doctor if your heart is racing persistently — a beta-blocker may be needed.
- In case of suspected overdose, call emergency services immediately; do not take epinephrine (EpiPen), as it can worsen the reaction.
Fainting, severe dizziness, or a very rapid heart rate that doesn't settle are signs to call your doctor right away. If you suspect an overdose — with symptoms like fainting, vomiting, or signs of shock — seek emergency care immediately.
Phenoxybenzamine warnings and precautions
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- Epinephrine must be avoided: Because phenoxybenzamine blocks alpha receptors, giving epinephrine (which stimulates both alpha and beta receptors) causes blood pressure to drop further — the opposite of what epinephrine normally does. This is called epinephrine reversal and is dangerous.
- Exaggerated low blood pressure with certain drugs: Any compound that stimulates both alpha and beta receptors can cause a severe drop in blood pressure and rapid heart rate when combined with this drug.
- Long-term use concerns: Extended use is not recommended due to potential carcinogenic (cancer-related) effects observed in laboratory studies. Your doctor will aim to limit the duration of treatment.
- Low blood pressure situations: Do not take this drug if you have a condition where a drop in blood pressure would be harmful.
Phenoxybenzamine interactions
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Phenoxybenzamine can interact with certain drugs in clinically important ways:
- Epinephrine (adrenaline): Contraindicated in overdose situations and dangerous in general — the alpha-blocking effect flips epinephrine's action, causing blood pressure to drop instead of rise (epinephrine reversal).
- Drugs that stimulate both alpha and beta receptors: Can cause an exaggerated drop in blood pressure and a very fast heart rate when taken with phenoxybenzamine.
- Levarterenol (norepinephrine): Phenoxybenzamine blocks levarterenol's ability to raise body temperature.
- Reserpine: Phenoxybenzamine blocks reserpine's ability to lower body temperature.
Interactions listed in the FDA-approved label
From the Phenoxybenzamine prescribing information (“Drug Interactions”): what the manufacturer studied or reported to the FDA.
- Compounds that stimulate both alpha- and beta-adrenergic receptors (i.e. epinephrine): Phenoxybenzamine hydrochloride may interact with them to produce an exaggerated hypotensive response and tachycardia. See WARNING
- Levarterenol: Phenoxybenzamine hydrochloride blocks hyperthermia production by levarterenol.
- Reserpine: Phenoxybenzamine hydrochloride blocks hypothermia production by reserpine.
Read the label’s full interactions text
Drug Interactions 2 – Phenoxybenzamine hydrochloride may interact with compounds that stimulate both alpha- and beta- adrenergic receptors (i.e. epinephrine) to produce an exaggerated hypotensive response and tachycardia (see WARNING ). Phenoxybenzamine hydrochloride blocks hyperthermia production by levarterenol, and blocks hypothermia production by reserpine.
Not a complete list. The label covers the interactions the manufacturer studied or reported, and our own interaction database does not cover every medicine either. Bring your full medication list, including vitamins and herbal products, to your pharmacist.
Before taking Phenoxybenzamine
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- Do not take phenoxybenzamine if your blood pressure is already low or if a drop in blood pressure would be dangerous for you.
- Do not take it if you are allergic to phenoxybenzamine hydrochloride or any component of the capsule.
- Tell your prescriber about every medication you take — especially epinephrine, reserpine, or any blood pressure or heart-rate drugs.
- Long-term use is not recommended; discuss with your doctor how long your treatment course should be and why.
Phenoxybenzamine overdose
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Taking too much phenoxybenzamine can cause a dangerous drop in blood pressure (especially when standing), a fast heart rate, vomiting, lethargy, and shock. If overdose is suspected, stop the medication and seek emergency medical care immediately. Standard blood-pressure-raising drugs (pressors) are not effective, and epinephrine must NOT be used — it will make blood pressure drop further. The effects of this drug are long-lasting, and a person may need to remain lying flat for 24 hours or more.
What Phenoxybenzamine does in the body
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Phenoxybenzamine produces what is called a "chemical sympathectomy" — it durably switches off the part of the nervous system that raises blood pressure and constricts blood vessels. This widens blood vessels, increases blood flow to the skin, mucous membranes, and abdominal organs, and lowers blood pressure in both lying-down and upright positions. Because only alpha receptors are blocked, beta receptors remain active and can be overstimulated if drugs like epinephrine are given.
How your body processes Phenoxybenzamine
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Only about 20–30% of an oral dose of phenoxybenzamine is absorbed in its active form. The half-life of the oral form is not precisely known, but when given intravenously the half-life is approximately 24 hours. Effects after intravenous administration can persist for at least 3 to 4 days, and with daily dosing, effects build up (accumulate) over nearly a week — meaning the drug's action is prolonged and cumulative.
Written from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →
Supplements & herbs that interact with Phenoxybenzamine
137 supplements and herbal products have documented interactions with Phenoxybenzamine in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 4
- Moderate · 112
- Minor · 21
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
Nutrient depletion considerations
Phenoxybenzamine has been associated with lower levels of 1 nutrient in the clinical literature. This does not mean a deficiency will occur — it means these may be worth discussing with your pharmacist or healthcare provider, especially with long-term use.
Educational information from a licensed clinical database (Natural Medicines) — not medical advice. Do not start or stop medications or supplements without professional guidance.
Phenoxybenzamine: pharmacist answers to common questions
Quick, plain-English answers to the questions patients ask most about Phenoxybenzamine — the kind of thing our pharmacy team would talk through with you at the counter.
What exactly is phenoxybenzamine used for?
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Will I feel dizzy when I stand up? What can I do about it?
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Why did my doctor say to avoid EpiPens while I'm on this?
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What side effects should I just expect versus ones that need a call to the doctor?
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My doctor mentioned not taking this long-term. Why?
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How will my doctor know if the dose is right for me?
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Is Phenoxybenzamine available over the counter?
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When was Phenoxybenzamine first available?
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Who makes Phenoxybenzamine?
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Answers drafted from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →
More about Phenoxybenzamine on HelloPharmacist
Phenoxybenzamine forms and strengths (how it comes)
Phenoxybenzamine is available in 1 form. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Capsule
How this form is used
- Used to control episodes of high blood pressure and sweating caused by pheochromocytoma
- May be used alongside a beta-blocker if heart rate becomes excessively fast during treatment
- Take capsules by mouth as directed by your prescriber — typically starting twice a day and adjusted gradually
- Dose is increased every other day until blood pressure is adequately controlled or side effects become a concern
- Long-term use is not recommended; follow your prescriber's guidance on duration
- Store at room temperature (68°F to 77°F); keep in a tightly closed container
Phenoxybenzamine on the U.S. market: products, makers and brands
How Phenoxybenzamine appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
6 companies list 6 Phenoxybenzamine product records with the FDA, mostly as capsule; the earliest marketing or approval year on record is 1953. Brand names on the directory include Dibenzyline; the rest are generics.
Also listed with the FDA, not a patient dose form: Powder (11) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.
Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
How widely Phenoxybenzamine is used (Medicaid data)
A general measure of how commonly Phenoxybenzamine is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Phenoxybenzamine is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Phenoxybenzamine prescribed? Of the 1,601 medications we measure, Phenoxybenzamine ranks #1,582 by Medicaid prescriptions — more than 1% of them.
Utilization by Phenoxybenzamine product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
phenoxybenzamine hydrochloride 10 MG Oral Capsule
Summed across the 1 of 11 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 861402
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Phenoxybenzamine, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 1 of 11 listed Phenoxybenzamine NDCs with Medicaid activity.
Compare Phenoxybenzamine products
A representative set of FDA-listed product records for Phenoxybenzamine — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Capsule | ||||
| 10 mg | Oral | Amneal Pharmaceuticals NY LLC | ANDA | View NDC → |
| 10 mg | Oral | Aurobindo Pharma Limited | ANDA | View NDC → |
| 10 mg | Oral | Burel Pharmaceuticals, LLC | ANDA | View NDC → |
| 10 mg | Oral | NorthStar Rx LLC | ANDA | View NDC → |
| 10 mg | Oral | Novitium Pharma LLC | ANDA | View NDC → |
| 10 mg | Oral | Rising Pharma Holdings, Inc. | ANDA | View NDC → |
Showing 6 of 6 products — FDA National Drug Code Directory. See every product, package size and price: browse all 6 Phenoxybenzamine NDCs →
Phenoxybenzamine side effects reported to the FDA (FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Phenoxybenzamine — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Phenoxybenzamine in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
Phenoxybenzamine FDA approval history
How Phenoxybenzamine went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
Phenoxybenzamine recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
The FDA’s enforcement reports list no Phenoxybenzamine recalls since July 2021.
✅No Phenoxybenzamine recalls on record since July 2021Source: FDA enforcement (recall) reports, via openFDA; our copy was last updated Sep 24, 2026.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 8149 2 dose forms · 2 strengths
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Dose form (SCDF) Injectable Solution RxCUI 385519No current FDA listingClinical drug / strength (SCD) hydrochloride 50 MG/MLRxCUI 150752 -
Dose form (SCDF) Oral Capsule RxCUI 373346In current FDA listingsClinical drug / strength (SCD) hydrochloride 10 MGRxCUI 861402
Look up RxCUI 8149 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
Phenoxybenzamine supply and shortage status
Whether Phenoxybenzamine is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
Phenoxybenzamine brand names
Phenoxybenzamine is sold under one brand name in the FDA directory — Dibenzyline. A brand and its generic contain the same active ingredient; the brand name belongs to one company's product.
Who makes Phenoxybenzamine: manufacturers and labelers
6 companies list Phenoxybenzamine products with the FDA. By number of product records, the largest are Amneal Pharmaceuticals NY LLC, Aurobindo Pharma Limited, Burel Pharmaceuticals, LLC. Labelers include manufacturers and repackagers; the product in your bottle depends on which one your pharmacy stocks.
Phenoxybenzamine drug class (RxNorm)
Phenoxybenzamine belongs to the alpha-Adrenergic Blocker class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
Sources for this Phenoxybenzamine page
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How this page is built
HelloPharmacist combines public FDA and NLM records and does not author the underlying clinical facts. The plain-language sections are written with AI from the FDA-approved label text and reviewed by our pharmacy team before publication. Amneal Pharmaceuticals NY LLC is the representative DailyMed label linked for verification and dates. This is general education, not medical advice: always talk to your doctor or pharmacist about your own medicines. How we build and review drug pages →