This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'Drug of choice for pheochromocytoma ? \nSelect and explain. \nA. Propranolol, B. Phenoxybenzamine, C. Prazosin, D. Nitroprosside', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Phenoxybenzamine Pharmacological treatment of pheochromocvtoma Preoperatively or when tumour cannot be removed, blood pressure control is achieved by a-adrenoreceptor blockade which reverses peripheral vasoconstriction - Phenoxybenzomine is the DOC For hypeensive crises or intraoperative control of BP, phentolamine is the DOC. Prazosin is an alternative. Nitroprusside can also be used-- Harrison 17th/e p. 1561. In adrenaline secreting tumors, if tachycardia persists, 13-blocker can be added after staing oc-blockers. ACE inhibitor or calcium channel blockers can be used when blood pressure is difficult to control with phenoxybenzamine alone. Metyrosine has been used with some success to block catecholamine synthesis in malignant pheochromocytoma. Metaiodobenzylguanidine (MIBG) is actively taken up by adrenergic tissue - 123I-MIBG can be used for selective therapeutic irradiation of functioning metastasis.", 'role': 'assistant'}]