Question

Why are beta-blockers contraindicated in the treatment of a pheochromocytoma?

Answer 1

Pheochromocytoma is extremely dangerous and life-threatening. The best treatment for pheochromocytoma is to surgically remove the adrenal gland with the tumor. Medical therapy to block the effects of adrenaline excess is available but is not nearly as effective as adrenalectomy. Medical therapy is used for preoperative preparation earlier to surgical resection for acute hypertensive crises, and as primary therapy for patients with metastatic pheochromocytomas. Preoperative preparation needs combined alpha and beta blockade to control the pressure of blood and to prevent an intra-operative hypertensive crisis.

Beta blockers are used if major tachycardia occurs after alpha blockade. Beta blockers are not controlled the sufficient alpha blockade has been established, because unrestricted alpha-adrenergic receptor stimulation precipitates a hypertensive crisis. Noncardioselective beta blockers, like as propranolol or nadolol are the usual choice, cardioselective agents, like as atenolol and metoprolol are used.

Labetalol is a noncardioselective beta-adrenergic blocker and selective alpha-adrenergic blocker, which shows effect in controlling hypertension that is associated with pheochromocytoma. It is associated with paradoxic episodes of hypertension thought to be secondary to incomplete alpha blockade. Therefore, its use in the preoperative treatment of patients with pheochromocytoma is controversial.

During surgery, intravenous phentolamine, Rapid-acting intravenous beta blockers, such as esmolol, are used to normalize blood pressure.