Phenoxybenzamine HCl
| (fen-ox-ee-BEN-zuh-meen HIGH-droe-KLOR-ide) |
| Dibenzyline |
| Class: Antihypertensive/Agent for pheochromocytoma |
Action Irreversibly blocks alpha-adrenergic receptors.
Indications Control of episodes of hypertension and sweating in patients with pheochromocytoma. Unlabeled use(s): Treatment of micturition disorders resulting from neurogenic bladder; treatment of functional outlet obstruction and partial prostatic obstruction.
Contraindications Conditions in which fall in BP may be undesirable.
ADULTS: PO 10 mg bid initially. Usual dosage range is 20 to 40 mg bid to tid. CHILDREN: PO 1 to 2 mg/kg/day in 3 to 4 divided doses.
Epinephrine: Exaggerated hypotensive response and tachycardia may occur when epinephrine, or other agents that stimulate both alpha- and beta-receptors, are given concomitantly with phenoxybenzamine.
Lab Test Interferences None well documented.
CV: Orthostatic hypotension; tachycardia. CNS: Drowsiness; fatigue. EENT: Miosis. GI: Gastrointestinal irritation. GU: Inhibition of ejaculation. RESP: Nasal congestion.
Pregnancy: Safety not established. Lactation: Undetermined. 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.
| PATIENT CARE CONSIDERATIONS |
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- Give drug with milk or in divided doses to reduce GI irritation.
- Store in airtight container and protect from light.
- Obtain patient history, including drug history and any known allergies.
- Instruct patient to change position slowly, especially from lying to sitting up or standing, and to dangle and move legs before standing.
- Assess for the following adverse reactions: Orthostatic hypotension, tachycardia, nasal congestion.
- Assess for effectiveness (lowering of BP) periodically.
- Take safety precautions if patient develops lightheadedness.
- If shocklike state develops, place patient in Trendelenburg position. Notify physician and begin emergency interventions.
- During dosage adjustments, monitor BP and pulse (eg, quality, rate, rhythm) with patient in lying and standing position for 4 days.
- In patients with peripheral vasospastic problems, observe for improvement in skin color, temperature, and quality of peripheral pulses.
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- 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 physician.
- 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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