Vasodilator drugs relax the smooth muscle in blood vessels, which causes the vessels to dilate. Dilation of arterial vessels leads to a reduction in systemic vascular resistance, which leads to a fall in arterial blood pressure. Dilation of venous vessels decreases venous blood pressure.
Vasodilators include Nitrates, ACE inhibitors, alpha 1 antagonist, Nitroprusside sodium, Ca antagonists, Dihydralazine and Minoxidil. Arteriolar vasodilators are given to lower blood pressure in hypertension. Venous vasodilators are used to reduce venous filling pressure (preload) in angina pectoris or cardiac failure.