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': "Agent of first choice in an acute attack of Prinzmetal's angina is - \nSelect and explain. \nA. Diltiazem, B. Nitrates, C. Propranolol, D. Verapamile", 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Nitrates Treatment of variant angina Drugs are : 1. Nitrates 2. Calcium channel blockers (verapamil, diltiazem) o Nitroglycerin is considered the drug of choice for the patient with variant angina. o Prazosin a selective a-blocker may also be used because it prevents a mediated vasospasm. o b-blocker's are contraindicated because they cause constriction of coronary aery due to unopposed a mediated vasoconstriction. Prevention of variant angina o In contrast Nitrates are not used for the prevention of variant angina because of delevelopment of tolerance. o CCBs are the DOC for prevention.", 'role': 'assistant'}]