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blood pressure should be lowered rapidly in patients with hypeensive encephalopathy, there are inherent risks of overly aggressive therapy. In hypeensive individuals, the upper and lower limits of autoregulation of cerebral blood flow are shifted to higher levels of aerial pressure, and rapid lowering of blood pressure to below the lower limit of autoregulation may precipitate cerebral ischemia or infarction as a consequence of decreasedcerebral blood flow. Renal and coronary blood flows also may decrease with overly aggressive acute therapy. The initial goal of therapy is to reduce mean aerial blood pressure by no more than 25% within minutes to 2 h or to a blood pressure in the range of 160/100-110 mmHg. This may be accomplished with IV nitroprusside, a sho-acting vasodilator with a rapid onset of action that allows for minute-to-minute control of blood pressure. Parenteral labetalol and nicardipine are also effective agents for the treatment of hypeensive encephalopathy. ref:Harrison&;s principles of internal medicine,ed 18,pg no 2059