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Pronunciation: fen-ox-ee-BEN-zuh-meen HIGH-droe-KLOR-ide
Class: Agent for pheochromocytoma
- Capsules 10 mg
Irreversibly blocks alpha-adrenergic receptors.
20% to 30% of an oral dose is absorbed in the active form.
Phenoxybenzamine hydrochloride metabolism is hepatic.
Phenoxybenzamine hydrochloride excretion is renal and biliary. The t 1/ 2 is approximately 24 h (IV); oral is unknown.
3 to 4 days (IV).
Indications and Usage
Control of episodes of hypertension and sweating in patients with pheochromocytoma.
Treatment of micturition disorders resulting from neurogenic bladder; treatment of functional outlet obstruction and partial prostatic obstruction.
Conditions in which fall in BP may be undesirable.
Dosage and AdministrationAdults
PO 10 mg bid initially. Usual dosage range is 20 to 40 mg 2 to 3 times daily.Children
PO 1 to 2 mg/kg/day in 3 to 4 divided doses.
Store in airtight container and protect from light.
Exaggerated hypotensive response and tachycardia may occur when epinephrine, or other agents that stimulate both alpha- and beta-receptors, are given concomitantly with phenoxybenzamine.
Laboratory Test Interactions
None well documented.
Orthostatic hypotension; tachycardia.
Inhibition of ejaculation.
Safety not established.
Special Risk Patients
Administer drug with caution to patients with marked cerebral or coronary arteriosclerosis or renal damage. Adrenergic blocking effects may aggravate respiratory infections.
Orthostatic hypotension, dizziness, fainting, tachycardia, vomiting, lethargy, shock.
- Advise patient to avoid alcoholic beverages.
- Stress to patient importance of weight reduction, sodium and alcohol restriction, discontinuation of smoking, regular exercise, and behavior modification.
- Instruct patient to avoid OTC cough, cold, or allergy medications containing sympathomimetics without consulting health care provider.
- Instruct patient to avoid sudden position changes to prevent orthostatic hypotension. Warn patient that taking a hot bath or shower may aggravate dizziness.
- Inform patient that drug may cause nasal congestion and constricted pupils.
- Advise patient that inhibition of ejaculation may occur, but reassure patient that this condition generally decreases with continued therapy.
- Advise patient that drug may cause drowsiness, and to use caution while driving or performing other tasks requiring mental alertness.
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