Acute Dose-Response Curve of Enalapril in Renovascular Hypertensives

We evaluated the acute blood pressure lowering effect of enalapril in terms of dose-response curve and compared this effect with that on humoral parameters. Eleven renovascular patients with acute angiotensin-converting enzyme (ACE) inhibition received (according to a randomized double-blind cross-over design) placebo, 10, 20, and 40 mg of enalapril with a 72-hour interval between each dose. Seated blood pressure and heart rate were measured every hour for 6 hours and then again at the twelfth and twenty-fourth hour, while venous blood samples for plasma renin activity, plasma aldosterone and serum ACE measurements were obtained at the fourth and twenty-fourth hour after receiving the placebo or drug. Blood pressure was significantly reduced by all three doses of enalapril at hour 4, while at hour 24 it was reduced only by the 20- and 40-mg doses. A significant correlation (r = 0.68; P less than 0.001) was found between percentage decrements of mean blood pressure and the log of the doses at hour 4 with a similar (although not significant) trend at hour 24. Plasma renin activity was significantly and to a similar extent increased by the three doses of enalapril at hour 4, while at hour 24 it was significantly increased only by the 40-mg dose. Serum ACE and plasma aldosterone were significantly reduced both at hours 4 and 24 without any difference between doses. No correlation was found between mean blood pressure changes and those of humoral factors.(ABSTRACT TRUNCATED AT 250 WORDS)