Medication Summary
Although surgical removal is the definitive treatment of pheochromocytoma, pharmacologic therapy plays a critical role in control of blood pressure, both perioperatively and long-term in patients with inoperable disease. Alpha-adrenergic antagonists and beta-adrenergic antagonists, often in combination, as well as nitrates are used for this purpose. Antiarrhythmic agents are used to control the ventricular tachyarrhythmias that these patients may experience.
Alpha-Adrenergic Blocking Agents
Class Summary
These agents are used preoperatively in combination with beta-blockers. At low doses, alpha-adrenergic receptor blockers may be used as monotherapy in the treatment of hypertension. At higher doses, the agents may cause sodium and fluid to accumulate. As a result, concurrent diuretic therapy may be required to maintain the hypotensive effects of the alpha-receptor blockers.
Phenoxybenzamine (Dibenzyline)
This alpha1- and alpha2-adrenergic blocking agent blocks circulating epinephrine and norepinephrine action, reducing hypertension. It decreases sympathetic tone on the vasculature, dilates blood vessels, and lowers arterial blood pressure. Long-acting properties produce and maintain a chemical sympathectomy. Phenoxybenzamine lowers supine and upright blood pressures. It does not affect the parasympathetic nervous system.
Phentolamine
Phentolamine is an alpha1- and alpha2-adrenergic blocking agent that blocks circulating epinephrine and norepinephrine action, reducing hypertension that results from catecholamine effects on the alpha-receptors. Drug action is transient and alpha-adrenergic blockade is incomplete. This agent is often used immediately prior to or during adrenalectomy to prevent or control paroxysmal hypertension that results from anesthesia, stress, or operative manipulation of the tumor. It is a first-line agent to treat hypertensive crisis.
Prazosin (Minipress)
Prazosin is a postsynaptic alpha1-antagonist. It decreases blood pressure with minimal risk of reflex tachycardia.
Beta-Adrenergic Blocking Agents
Class Summary
These agents are used as adjunctive therapy for cardiac effects. The agents inhibit chronotropic, inotropic, and vasodilatory responses to beta-adrenergic stimulation.
Propranolol (Inderal LA, InnoPran XL)
Propranolol is a nonselective beta-adrenergic receptor blocker. After primary treatment with an alpha-receptor blocker, propranolol may be used as adjunctive therapy if control of tachycardia becomes necessary before or during surgery.
This agent may be used to treat excessive beta-receptor stimulation in patients with inoperable metastatic pheochromocytoma. It has membrane-stabilizing activity and decreases automaticity of contractions. It decreases the effects of the sympathetic nervous system on the heart and juxtaglomerular apparatus, release of renin, and blood pressure. It acts in the CNS to reduce sympathetic outflow and vasoconstrictor tone. Propranolol is not suitable for emergency treatment of hypertension; do not administer IV in hypertensive emergencies.
Labetalol (Trandate)
Labetalol blocks beta1-, alpha-, and beta2-adrenergic receptor sites, thus decreasing blood pressure.
Esmolol (Brevibloc)
Esmolol is an excellent drug for use in patients at risk for experiencing complications from beta-blockade, particularly those with reactive airway disease, mild-to-moderate LV dysfunction, and/or peripheral vascular disease. Its short half-life of 8 min allows for titration to desired effect and quick discontinuation if needed.
Vasodilators
Class Summary
These agents provide peripheral and coronary vasodilation.
Sodium nitroprusside (Nitropress)
Sodium nitroprusside acts directly on vascular smooth muscle to cause vasodilatation and reduce blood pressure. It also has a positive inotropic effect.
Antiarrhythmic Agents
Class Summary
These agents alter the electrophysiologic mechanisms responsible for arrhythmia.
Amiodarone (Cordarone, Pacerone, Nexterone)
Amiodarone may inhibit atrioventricular (AV) conduction and sinus node function. This agent prolongs action potential and refractory period in myocardium and inhibits adrenergic stimulation. Before administration, control the ventricular rate and CHF (if present) with digoxin or calcium channel blockers.
Lidocaine (Xylocaine)
Lidocaine is a class IB antiarrhythmic that increases electrical stimulation threshold of the ventricle, suppressing automaticity of conduction through the tissue.
Radiopharmaceuticals
Class Summary
Iobenguane I 131 is the first drug approved by the FDA for rare tumors of the adrenal gland (pheochromocytoma or paraganglioma) that cannot be removed by surgery.
Iobenguane I 131 (Azedra)
Iobenguane is similar in structure to the neurotransmitter norepinephrine (NE) and is subject to the same uptake and accumulation pathways as NE. Iobenguane is taken up by the NE transporter in adrenergic nerve terminals and accumulates in adrenergically innervated tissues (eg, heart, lungs, adrenal medulla, salivary glands, liver, spleen) as well as tumors of neural crest origin. Following IV administration and cell uptake, radiation resulting from radioactive decay of I 131 causes cell death and tumor necrosis.
Iobenguane I 131 is indicated in adults and children aged 12 years or older for iobenguane scan–positive, unresectable, locally advanced or metastatic pheochromocytoma or paraganglioma who require systemic anticancer therapy.
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Axial, T2-weighted MRI scan showing large left suprarenal mass of high signal intensity on a T2-weighted image. The mass is a pheochromocytoma.
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Abdominal CT scan demonstrating left suprarenal mass of soft tissue attenuation representing a paraganglioma.
