Drug of choice for pheochromocytoma –
**Core Concept**
Pheochromocytoma is a rare, usually benign, tumor of the adrenal gland that secretes excess catecholamines, leading to hypertension, tachycardia, and other cardiovascular symptoms. The primary goal of pharmacological management is to control blood pressure and prevent hypertensive crises.
**Why the Correct Answer is Right**
The drug of choice for pheochromocytoma is a non-selective alpha and beta blocker due to its ability to control the sudden surges in catecholamines and prevent hypertensive crises. Phenoxybenzamine, a non-selective alpha blocker, is the preferred initial agent because it inhibits the alpha-1 adrenergic receptors, which are responsible for vasoconstriction. This allows for the reduction of blood pressure without causing reflex tachycardia. Once the blood pressure is controlled, a beta blocker such as propranolol can be added to prevent tachycardia and further reduce blood pressure.
**Why Each Wrong Option is Incorrect**
**Option A:** Metoprolol is a selective beta-1 blocker that can cause unopposed alpha receptor stimulation, leading to increased blood pressure and hypertensive crises.
**Option B:** Clonidine is an alpha-2 agonist that can cause bradycardia and hypotension, making it unsuitable for pheochromocytoma management.
**Option C:** Hydralazine is a direct vasodilator that can cause reflex tachycardia and is not a first-line agent for pheochromocytoma.
**Clinical Pearl / High-Yield Fact**
When managing pheochromocytoma, it's essential to start with a non-selective alpha blocker to prevent hypertensive crises, followed by a beta blocker to control tachycardia. This sequence is crucial to prevent cardiovascular complications.
**Correct Answer: C. Phenoxybenzamine**