Version July 2025
Pheochromocytoma, preoperative management: Limited data available: Children and Adolescents: Oral: Initial: 0.2 to 0.25 mg/kg/dose once or twice daily; maximum dose: 10 mg/dose; slowly titrate (eg, every 4 days) to effect; increments of 0.2 mg/kg/day have been reported; reported maintenance dose range: 0.4 to 3 mg/kg/day in divided doses every 6 to 8 hours; maximum single maintenance dose: 40 mg/dose; maximum daily dose: 4 mg/kg/day (Ref).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
There are no dosage adjustments provided in manufacturer’s labeling. Use with caution.
There are no dosage adjustments provided in manufacturer’s labeling.
(For additional information see "Phenoxybenzamine: Drug information")
Pheochromocytoma: Oral: Initial: 10 mg twice daily; may increase slowly every other day until optimal blood pressure response is achieved; usual dosage range: 20 to 40 mg 2 to 3 times daily. Doses up to 240 mg daily have been reported (Ref).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
There are no dosage adjustments provided in the manufacturer's labeling; use with caution.
There are no dosage adjustments provided in the manufacturer's labeling.
The following adverse drug reactions are derived from product labeling unless otherwise specified.
Postmarketing:
Cardiovascular: Edema (van der Zee 2014), orthostatic hypotension (van der Zee 2014), tachycardia (van der Zee 2014)
Gastrointestinal: Gastrointestinal irritation
Genitourinary: Inhibited ejaculation
Nervous system: Drowsiness, fatigue
Ophthalmic: Miosis
Respiratory: Nasal congestion (van der Zee 2014)
Hypersensitivity to drug or any component of the formulation; conditions in which a fall in blood pressure may be undesirable.
Concerns related to adverse effects:
• Cardiovascular effects: An exaggerated hypotensive response and tachycardia may occur when administered concurrently with compounds that stimulate both alpha- and beta-adrenergic receptors.
Disease-related concerns:
• Cardiovascular disease: Use with caution in patients with marked cerebral or coronary atherosclerosis.
• Renal impairment: Use with caution in patients with renal impairment.
• Respiratory infection: May aggravate symptoms of respiratory infections.
Dosage form specific issues:
• Benzyl alcohol and derivatives: Some dosage forms may contain benzyl alcohol; large amounts of benzyl alcohol (≥99 mg/kg/day) have been associated with a potentially fatal toxicity ("gasping syndrome") in neonates; the "gasping syndrome" consists of metabolic acidosis, respiratory distress, gasping respirations, CNS dysfunction (including convulsions, intracranial hemorrhage), hypotension, and cardiovascular collapse (AAP ["Inactive" 1997]; CDC, 1982); some data suggest that benzoate displaces bilirubin from protein binding sites (Ahlfors 2001); avoid or use dosage forms containing benzyl alcohol with caution in neonates. See manufacturer's labeling.
Other warnings/precautions:
• Long-term use: Not recommended for long-term use due to case reports of cancer in humans; carefully weigh the risk and benefits before use.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Capsule, Oral, as hydrochloride:
Dibenzyline: 10 mg [contains fd&c yellow #6 (sunset yellow)]
Generic: 10 mg
Yes
Capsules (Dibenzyline Oral)
10 mg (per each): $24.00
Capsules (Phenoxybenzamine HCl Oral)
10 mg (per each): $129.45 - $134.99
Disclaimer: A representative AWP (Average Wholesale Price) price or price range is provided as reference price only. A range is provided when more than one manufacturer's AWP price is available and uses the low and high price reported by the manufacturers to determine the range. The pricing data should be used for benchmarking purposes only, and as such should not be used alone to set or adjudicate any prices for reimbursement or purchasing functions or considered to be an exact price for a single product and/or manufacturer. Medi-Span expressly disclaims all warranties of any kind or nature, whether express or implied, and assumes no liability with respect to accuracy of price or price range data published in its solutions. In no event shall Medi-Span be liable for special, indirect, incidental, or consequential damages arising from use of price or price range data. Pricing data is updated monthly.
A 2 mg/mL oral suspension may be made with capsules, propylene glycol 1%, and citric acid 0.15% in distilled water. Prepare the vehicle by dissolving 150 mg citric acid in a minimal amount of distilled water. Add 1 mL propylene glycol and mix well; add quantity of distilled water sufficient to make 100 mL (only a small portion of this vehicle will be used to make the final product). Grind the contents of two phenoxybenzamine 10 mg capsules in a mortar and reduce to a fine powder. Add a small portion of the vehicle and mix to a uniform paste; transfer to a graduated cylinder, rinse mortar with vehicle, and add quantity of prepared vehicle sufficient to make 10 mL. Transfer to an amber glass prescription bottle with tight-fitting cap; label "shake well" and "refrigerate". Stable for 7 days when stored in amber glass prescription bottles and refrigerated.
A stock solution of 10 mg/mL in propylene glycol was stable for 30 days refrigerated. When this stock solution was diluted 1:4 (v/v) with syrup (66.7% sucrose) to 2 mg/mL, the preparation was stable for 1 hour refrigerated. Note: Although the stock solution is stable for 30 days, it must be diluted before administration to decrease the amount of propylene glycol delivered to the patient.
Oral: Administer without regard to meals; may administer with milk to decrease GI upset
Hazardous agent (NIOSH 2024 [table 2]).
Use appropriate precautions for receiving, handling, storage, preparation, dispensing, transporting, administration, and disposal. Follow NIOSH and USP 800 recommendations and institution-specific policies/procedures for appropriate containment strategy (NIOSH 2023; NIOSH 2024; USP-NF 2020).
Note: Facilities may perform risk assessment of some hazardous drugs to determine if appropriate for alternative handling and containment strategies (USP-NF 2020). Refer to institution-specific handling policies/procedures.
Store at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F).
Treatment of hypertension and sweating in patients with pheochromocytoma (FDA approved in adults)
Phenoxybenzamine may be confused with phenazopyridine
None known.
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the drug interactions program by clicking on the “Launch drug interactions program” link above.
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the drug interactions program
Alpha-/Beta-Agonists: Alpha1-Blockers may decrease therapeutic effects of Alpha-/Beta-Agonists. Risk C: Monitor
Alpha1-Blockers: May increase antihypertensive effects of Alpha1-Blockers. Risk X: Avoid
Amifostine: Blood Pressure Lowering Agents may increase hypotensive effects of Amifostine. Management: When used at chemotherapy doses, hold blood pressure lowering medications for 24 hours before amifostine administration. If blood pressure lowering therapy cannot be held, do not administer amifostine. Use caution with radiotherapy doses of amifostine. Risk D: Consider Therapy Modification
Amphetamines: May decrease antihypertensive effects of Antihypertensive Agents. Risk C: Monitor
Antipsychotic Agents (Second Generation [Atypical]): Blood Pressure Lowering Agents may increase hypotensive effects of Antipsychotic Agents (Second Generation [Atypical]). Risk C: Monitor
Arginine: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Barbiturates: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Benperidol: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Brigatinib: May decrease antihypertensive effects of Antihypertensive Agents. Brigatinib may increase bradycardic effects of Antihypertensive Agents. Risk C: Monitor
Brimonidine (Topical): May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Bromperidol: May decrease hypotensive effects of Blood Pressure Lowering Agents. Blood Pressure Lowering Agents may increase hypotensive effects of Bromperidol. Risk X: Avoid
Dapoxetine: May increase orthostatic hypotensive effects of Alpha1-Blockers. Risk C: Monitor
Dexmethylphenidate: May decrease therapeutic effects of Antihypertensive Agents. Risk C: Monitor
Diazoxide: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
DULoxetine: Blood Pressure Lowering Agents may increase hypotensive effects of DULoxetine. Risk C: Monitor
Flunarizine: May increase therapeutic effects of Antihypertensive Agents. Risk C: Monitor
Herbal Products with Blood Pressure Increasing Effects: May decrease antihypertensive effects of Antihypertensive Agents. Risk C: Monitor
Herbal Products with Blood Pressure Lowering Effects: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Hypotension-Associated Agents: Blood Pressure Lowering Agents may increase hypotensive effects of Hypotension-Associated Agents. Risk C: Monitor
Iloperidone: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Isocarboxazid: May increase antihypertensive effects of Antihypertensive Agents. Risk X: Avoid
Levodopa-Foslevodopa: Blood Pressure Lowering Agents may increase hypotensive effects of Levodopa-Foslevodopa. Risk C: Monitor
Levomethadone: May increase hypotensive effects of Alpha1-Blockers (Nonselective). Risk C: Monitor
Loop Diuretics: May increase hypotensive effects of Antihypertensive Agents. Risk C: Monitor
Lormetazepam: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Metergoline: May decrease antihypertensive effects of Blood Pressure Lowering Agents. Blood Pressure Lowering Agents may increase orthostatic hypotensive effects of Metergoline. Risk C: Monitor
Methylphenidate: May decrease antihypertensive effects of Antihypertensive Agents. Risk C: Monitor
Midodrine: Alpha1-Blockers (Nonselective) may decrease therapeutic effects of Midodrine. Risk C: Monitor
Molsidomine: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Nicorandil: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Nitroprusside: Blood Pressure Lowering Agents may increase hypotensive effects of Nitroprusside. Risk C: Monitor
Obinutuzumab: May increase hypotensive effects of Blood Pressure Lowering Agents. Management: Consider temporarily withholding blood pressure lowering medications beginning 12 hours prior to obinutuzumab infusion and continuing until 1 hour after the end of the infusion. Risk D: Consider Therapy Modification
Pentoxifylline: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Perazine: May increase hypotensive effects of Antihypertensive Agents. Risk C: Monitor
Phenylephrine (Systemic): Alpha1-Blockers may decrease vasoconstricting effects of Phenylephrine (Systemic). Risk C: Monitor
Pholcodine: Blood Pressure Lowering Agents may increase hypotensive effects of Pholcodine. Risk C: Monitor
Phosphodiesterase 5 Inhibitors: May increase hypotensive effects of Alpha1-Blockers (Nonselective). Management: Ensure patient is stable on one agent prior to initiating the other, and always initiate combination using the lowest possible dose of the drug being added. When tadalafil is used for treatment of BPH, concurrent alpha 1-blockers are not recommended. Risk D: Consider Therapy Modification
Prostacyclin Analogues: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Quinagolide: May increase hypotensive effects of Blood Pressure Lowering Agents. Risk C: Monitor
Rilmenidine: Alpha1-Blockers may increase hypotensive effects of Rilmenidine. Risk C: Monitor
It is not known whether phenoxybenzamine can affect reproduction capacity.
Adequate animal reproduction studies have not been conducted. It is not known whether phenoxybenzamine can cause fetal harm when administered to a pregnant woman.
Blood pressure, orthostasis, heart rate
Produces long-lasting noncompetitive alpha-adrenergic blockade of postganglionic synapses in exocrine glands and smooth muscle; relaxes urethra and increases opening of the bladder
Onset of action: Within 2 hours; Maximum effect: Within 4 to 6 hours
Duration: IV: ≥3 to 4 days
Distribution: Distributes to and may accumulate in adipose tissues
Bioavailability: 20% to 30%
Half-life elimination: IV: ~24 hours
Excretion: Primarily in urine and bile
