This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
[{'content': 'Which of the following antihypeensive cause sedation \nSelect and explain. \nA. Clonidine, B. Hydralizine, C. Losaan, D. Amilodipine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Refer kDT 6/e p546 The classic centrally acting antihypeensives such as clonidine, guanfacine and alpha-methyl-DOPA ( its active metabolite alpha-methyl-noradrenaline) induce peripheral sympathoinhibition and a fall in blood pressure as a result of alpha2-adrenoceptor stimulation in the brain stem. These drugs have lost much of their clinical impoance because of their unourable side-effects (sedation, dry mouth, impotence), which are also mediated by alpha2-adrenoceptors, although in other anatomical regions', 'role': 'assistant'}]