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 (Kinney 2000).
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.
(For additional information see "Phenoxybenzamine: Pediatric drug information")
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 (Gal 2007; Hack 1999; Romero 2015; Sperling 2014)
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.
Refer to adult dosing.
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
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).
Pheochromocytoma: Treatment of sweating and hypertension associated with pheochromocytoma.
Phenoxybenzamine may be confused with phenazopyridine
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified. Frequency not defined.
Cardiovascular: Orthostatic hypotension, tachycardia
Central nervous system: Drowsiness, fatigue, inhibited ejaculation
Gastrointestinal: Gastrointestinal irritation
Ophthalmic: Miosis
Respiratory: Nasal congestion
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.
None known.
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
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
Beta-Blockers: May enhance the orthostatic hypotensive effect of Alpha1-Blockers. The risk associated with ophthalmic products is probably less than systemic products. 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
Calcium Channel Blockers: Alpha1-Blockers may enhance the hypotensive effect of Calcium Channel Blockers. Risk C: Monitor therapy
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
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-Containing Products: Blood Pressure Lowering Agents may enhance the hypotensive effect of Levodopa-Containing Products. 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.
It is not known if phenoxybenzamine is excreted in breast milk. Due to the potential for serious adverse reactions in the nursing infant, the manufacturer recommends a decision be made to discontinue nursing or to discontinue the drug, taking into account the importance of treatment to the mother.
Blood pressure, pulse, orthostatics
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
Capsules (Dibenzyline Oral)
10 mg (per each): $78.40
Capsules (Phenoxybenzamine HCl Oral)
10 mg (per each): $129.45 - $134.99
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