Final answer:
Phenoxybenzamine is the nonselective α-antagonist used in the preoperative preparation of a patient with pheochromocytoma to control hypertension by irreversibly blocking alpha receptors. Option A is correct.
Step-by-step explanation:
Preoperative Preparation for Pheochromocytoma
The student asked which nonselective α-antagonist is used in the preoperative preparation of a patient with pheochromocytoma. The answer to this question is phenoxybenzamine. Phenoxybenzamine is a sympatholytic drug that is used to treat hypertension related to pheochromocytoma by irreversibly binding to the alpha receptors, which leads to vasodilation and a decrease in blood pressure.
This makes it an effective preoperative medication to control hypertension before surgical removal of the pheochromocytoma. Drugs like doxazosin and terazosin are also α-antagonists, but they are selective rather than nonselective. Propranolol is a β-blocker, which is not the correct category of medication we are looking for in this context.
Phenoxybenzamine helps in reducing the risk of hypertensive crises, which can be precipitated by the manipulation of the tumor during surgery, by blocking the effects of epinephrine and norepinephrine on α-receptors.