Sodium nitroprusside (Ro 21-2498) is a potent vasodilator working through releasing NO spontaneously in blood. In Vitro: Sodium nitroprusside (Ro 21-2498) is a potent vasodilator. Sodium nitroprusside has potent vasodilating effects in arterioles and venules. Sodium nitroprusside breaks down in circulation to release nitric oxide (NO). NO activates guanylate cyclase in vascular smooth muscle and increases intracellular production of cGMP. The end result is vascular smooth muscle relaxation, which allow vessels to dilate [1]. Sodium nitroprusside decreases the proliferation of vascular smooth muscle cells [2]. Sodium nitroprusside (5 mg/kg) significantly reduces the intestinal ischemiareperfusion injury as a nitric oxide donor in rats [3].