Phenoxybenzamine

It is a powerful, alpha-adrenoreceptor blocking agent with a long duration of action.

Indications

Hypertensive episodes associated with pheochromocytoma; when pulmonary pressure is more than systemic pressure; peripheral vascular disorders due to vasospasm.

Dosage

Pheochromocytoma: adults: orally: initially 10mg once or twice daily, increased gradually according to the patient's response to a dose of 1-2 mg per kg body weight daily in 2 divided doses. IV : 1mg/kg intravenously in 200ml of 0.9% NaCl, infused over atleast 2 hours. Concomitant beta-adrenergic blockage may be necessary to control tachyacardia and arrhythmias when pheochromocytomas are excreting an appreciable amount of adrenaline as well as noradrenaline. 0.5 to 1mg per kg of the body weig

Contra-Indications

Cerebrovascular accidents, recovery period following acute myocardial infarction.

Special Precautions

Pregnancy, lactation, cerebral or coronary arteriosclerosis or renal damage, tachycardia or hypotension. Adrenergic blocking effect may aggravate symptoms of respiratory infections.

Side Effects

Nasal congestion, GI irritation, meiosis, postural hypotension with dizziness, fatigue and compensatory tachycardia, inhibition of ejaculation may occur.

Drug Interactions

Phenoxybenzamine hydrochloride may interact with compounds that stimulate both alpha- and beta-adrenergic receptors to produce an exaggerated hypotensive response and tachycardia. Dibenzyline (phenoxybenzamine) blocks hyperthermia production by levarterenol, and blocks hypothermia production by reserpine.