<s>[INST] context: in Aoic dissection Nitroprusside, esmolol, labetalol etc are those drugs which are more effective when given parenterally.Chronic aoic dissections are associated with weakening of the aoic wall that may lead to the development of aneurysmal dilatation.Aoic dissection is caused by a circumferential or, less frequently, transverse tear of the intima. It often occurs along the right lateral wall of the ascending aoa where the hydraulic shear stress is high. Another common site is the descendingthoracic aoa just below the ligamentum aeriosum.For acute dissection, unless contraindicated, b-adrenergic blockers should be administered parenterally, using intravenous propranolol, metoprolol, or the sho-acting esmolol to achieve a hea rate of approximately 60 beats/min. This should be accompanied by sodium nitroprusside infusion to lower systolic blood pressure to <=120 mmHg. Labetalol ( Chap. 247 ), a drug with both b- and a-adrenergic blocking propeies, also may be used as a parenteral agent in acute therapy for dissection. The calcium channel antagonists verapamil and diltiazem may be used intravenously if nitroprusside or b-adrenergic blockers cannot be employed. The addition of a parenteral angiotensinconveing enzyme (ACE) inhibitor such as enalaprilat to a b-adrenergic blocker also may be considered. Isolated use of a direct vasodilator such as hydralazine is contraindicated because these agents can increase hydraulic shear and may propagate the dissection. ref:Harrison&;s principles of internal medicine,ed 18,pg no 2064 [/INST] question: In Aoic dissection drug used are- | options: A: Propanolol B: Diazoxide C: Na nitroprusside D: Hydralazine | answer: A </s>