Version May 2024
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 2016 [group 2]).
Use appropriate precautions for receiving, handling, administration, and disposal. Gloves (single) should be worn during receiving, unpacking, and placing in storage.
NIOSH recommends single gloving for administration of intact tablets or capsules. If manipulating tablets/capsules (eg, to prepare an oral suspension), NIOSH recommends double gloving, a protective gown, and preparation in a controlled device; if not prepared in a controlled device, respiratory and eye/face protection as well as ventilated engineering controls are recommended. NIOSH recommends double gloving, a protective gown, and (if there is a potential for vomit or spit up) eye/face protection for administration of an oral liquid/feeding tube administration (NIOSH 2016). Assess risk to determine appropriate containment strategy (USP-NF 2017).
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 Lexicomp drug interactions program by clicking on the “Launch drug interactions program” link above.
Alpha-/Beta-Agonists: Alpha1-Blockers may diminish the vasoconstricting effect of Alpha-/Beta-Agonists. Similarly, Alpha-/Beta-Agonists may antagonize Alpha1-Blocker vasodilation. Risk C: Monitor therapy
Alpha1-Agonists: Alpha1-Blockers may diminish the vasoconstricting effect of Alpha1-Agonists. Similarly, Alpha1-Agonists may antagonize Alpha1-Blocker vasodilation. Risk C: Monitor therapy
Alpha1-Blockers: May enhance the antihypertensive effect of other Alpha1-Blockers. Risk X: Avoid combination
Amifostine: Blood Pressure Lowering Agents may enhance the hypotensive effect 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 diminish the antihypertensive effect of Antihypertensive Agents. Risk C: Monitor therapy
Antipsychotic Agents (Second Generation [Atypical]): Blood Pressure Lowering Agents may enhance the hypotensive effect of Antipsychotic Agents (Second Generation [Atypical]). Risk C: Monitor therapy
Arginine: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Barbiturates: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Benperidol: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Brigatinib: May diminish the antihypertensive effect of Antihypertensive Agents. Brigatinib may enhance the bradycardic effect of Antihypertensive Agents. Risk C: Monitor therapy
Brimonidine (Topical): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Bromperidol: May diminish the hypotensive effect of Blood Pressure Lowering Agents. Blood Pressure Lowering Agents may enhance the hypotensive effect of Bromperidol. Risk X: Avoid combination
Dapoxetine: May enhance the orthostatic hypotensive effect of Alpha1-Blockers. Risk C: Monitor therapy
Dexmethylphenidate: May diminish the therapeutic effect of Antihypertensive Agents. Risk C: Monitor therapy
Diazoxide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
DULoxetine: Blood Pressure Lowering Agents may enhance the hypotensive effect of DULoxetine. Risk C: Monitor therapy
Flunarizine: May enhance the therapeutic effect of Antihypertensive Agents. Risk C: Monitor therapy
Herbal Products with Blood Pressure Increasing Effects: May diminish the antihypertensive effect of Antihypertensive Agents. Risk C: Monitor therapy
Herbal Products with Blood Pressure Lowering Effects: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Hypotension-Associated Agents: Blood Pressure Lowering Agents may enhance the hypotensive effect of Hypotension-Associated Agents. Risk C: Monitor therapy
Levodopa-Foslevodopa: Blood Pressure Lowering Agents may enhance the hypotensive effect of Levodopa-Foslevodopa. Risk C: Monitor therapy
Loop Diuretics: May enhance the hypotensive effect of Antihypertensive Agents. Risk C: Monitor therapy
Lormetazepam: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Methylphenidate: May diminish the antihypertensive effect of Antihypertensive Agents. Risk C: Monitor therapy
Molsidomine: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Nicorandil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Nitroprusside: Blood Pressure Lowering Agents may enhance the hypotensive effect of Nitroprusside. Risk C: Monitor therapy
Obinutuzumab: May enhance the hypotensive effect 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 enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Pholcodine: Blood Pressure Lowering Agents may enhance the hypotensive effect of Pholcodine. Risk C: Monitor therapy
Phosphodiesterase 5 Inhibitors: May enhance the hypotensive effect 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 enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Quinagolide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Rilmenidine: Alpha1-Blockers may enhance the hypotensive effect of Rilmenidine. Risk C: Monitor therapy
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
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