This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disorders of Adrenal Gland, Subject name: Medicine
[{'content': 'What is the drug of choice for management of hypeension in Pheochromocytoma? \nSelect and explain. \nA. Phenoxybenzamine, B. Phentolamine, C. Labetalol, D. Esmolol', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Preoperative patient preparation is essential for safe surgery. a- Adrenergic blockers (Phenoxybenzamine) should be initiated at relatively low doses (e.g. 5-10 mg orally three times per day) and increased as tolerated every few days. Adequate alpha blockade generally requires 7 days, with a typical final dose of 20-30 mg phenoxybenzamine three times per day.', 'role': 'assistant'}]