Review Question - QID 212847

This patient with intermittent headaches, palpitations, perspiration, and pallor most likely has a pheochromocytoma, which is treated initially with an irreversable alpha-antagonist (e.g. phenoxybenzamine), followed by beta-blockers.

Pheochromocytomas are non-malignant tumors of the adrenal medulla and are the most common adrenal tumor in adults. Pheochromocytomas secrete catecholamines, thereby causing the symptoms of increased blood pressure, headaches, perspiration, tachycardia, and pallor (5 P’s: Pressure, Pain, Perspiration, Palpitations, and Pallor). Treatment of pheochromocytoma occurs in this sequence of events: 1) phenoxybenzamine, an irreversible alpha-antagonist (administered first to prevent unopposed alpha-receptor agonism if beta-receptors are blocked), 2) beta-blocker, and 3) surgical tumor resection.

Incorrect Answers:
Answer 2: Phentolamine is a reversible alpha-antagonist and is used for severe cocaine-induced hypertension as well as given to patients on MAO inhibitors who eat tyramine-containing foods.

Answer 3: Pilocarpine is a cholinomimetic agent that is used in the treatment of open-angle and closed-angle glaucoma.

Answer 4: Prazosin is an alpha-1 selective blocker that can be used to treat the urinary symptoms of benign prostatic hyperplasia, post-traumatic stress disorder PTSD, and hypertension.

Answer 5: Propanolol is a beta-blocker that is used in the treatment of pheochromocytoma after administration of an irreversible alpha-antagonist. Beta blockers can cause unopposed alpha-1 receptor agonism if given alone for pheochromocytoma.

Bullet Summary:
The first step in treating pheochromocytoma is an irreversible alpha antagonist, such as phenoxybenzamine.