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 not used in prinzmetal angina is? \nSelect and explain. \nA. Propranolol, B. Propranolol, C. Nitritesrites, D. Isosorbide dinitrate', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Propranolol o P-blocker's are contraindicated because they cause constriction of coronary aery due to unopposed a mediated vasoconstriction.", 'role': 'assistant'}]