Abstract
Beta-blockers without intrinsic sympathomimetic action have been reported to produce an increase in peripheral vascular resistance. The present study was designed to determine the effects of a new beta-blocker, nipradilol (3,4-dihydro-8-(-hydroxy-3-isopropylamino) propoxy-3-nitroxy-2H-1-benzopyran), on forearm blood flow (FBF) in seven patients (mean age, 51.6 ± 6.7 years) with essential hypertension. After overnight fasting, FBF was determined using venous occlusion strain-gauge plethysmography before and two hours after oral administration of 6 mg nipradilol or 20 mg propranolol. Both beta-blokers produced a significant decrease in blood pressure, and heart rate also tended to decrease. As a result, the product obtained by multiplying systolic blood pressure by heart rate was reduced after both nipradilol and propranolol. Nipradilol increased FBF from 0.78 ± 0.10 ml/100 ml/min to 1.72 ± 0.28 ml/100 ml/min ( P < 0.02), while propranolol decreased FBF (from 0.99 ± 0.29 ml/100 ml/min to 0.73 ± 0.24 ml/100 ml/min, P < 0.02). Vascular resistance, calculated by dividing mean blood pressure by FBF, was reduced significantly to 46% of control levels with nipradilol, although propranolol elevated vascular resistance by 39%. These results suggest that nipradilol dilates peripheral vessels, possibly through the action of its nitroester residue or by concomitant alpha 1-blocking activity.
Published Version
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