Acute effect of labetalol on hypertensive brachial artery.

Forearm arterial hemodynamics, including measurements of brachial artery diameter and compliance with pulsed Doppler velocimetry, were determined before and after acute administration of labetalol in patients with sustained essential hypertension. Labetalol caused a significant and rapid drop in blood pressure, with a decrease in forearm vascular resistance and an increase in brachial blood flow. Brachial artery diameter did not change, whereas arterial compliance increased significantly. The study provided evidence that labetalol caused a shift of the pressure-brachial artery diameter curve toward lower values of blood pressure, indicating a pharmacological effect of alpha and beta blockade on the hypertensive arterial wall.