Action of vasodilating drugs on small and large arteries of hypertensive patients.

We studied blood pressure, arterial diameter, and blood flow of the brachial artery in patients with sustained essential hypertension before and after administration of the vasodilating drugs nitroglycerin, captopril, dihydralazine, diltiazem, and isosorbide dinitrate (ISDN). The diameter and the blood flow of the brachial artery were measured with a pulsed Doppler device which allowed the angle between the ultrasound beam and the vessel axis to be determined with a precision better than 2%. Nitroglycerin and captopril decreased blood pressure slightly but increased arterial diameter markedly. Dihydralazine, diltiazem, and ISDN decreased blood pressure similarly and significantly and also reduced forearm vascular resistance. Dihydralazine reduced arterial diameter (p less than 0.001), but did not change brachial blood flow. Diltiazem and ISDN increased the arterial diameter markedly (p less than 0.001 and p less than 0.01, respectively), but only the former increased brachial blood flow. We conclude that antihypertensive drugs that dilate small arteries can either reduce (dihydralazine) or increase (nitroglycerin, captopril, diltiazem, ISDN) the caliber of large peripheral arteries and thus have different effects on peripheral blood flow.