Vasodilators in the treatment of hypertension

Vasodilators lower the blood pressure by decreasing total peripheral resistance. The hemodynamic changes depend on the mix between arteriolar and venous dilatation. Since the compensatory responses are blunted with sympatholytic agents and diuretics, vasodilators can be applied effectively in the treatment of hypertension. Hydralazine and prazosin are used as step III drugs in combination with beta-adrenergic blockers and diuretics. Only hypertensive patients whose blood pressure is not controlled by standard antihypertensive drugs should receive minoxidil or captopril. Hypertensives receiving minoxidil usually require a loop diuretic such as furosemide, in addition to a beta-blocker. Captopril is usually combined with a thiazide diuretic and frequently also with a beta-adrenergic blocker. For hypertensive emergencies diazoxide must be injected intravenously as a bolus. It is contraindicated in patients with dissecting aortic aneurysm or left ventricular failure. Sodium nitroprusside is effective in most cases of hypertensive crisis and must be administered intravenously under continuous observation.