SUMMARY Nine patients with uncomplicated essential hypertension received, according to a randomized sequence, captopril (25 mg three times daily), nifedipine (10 mg three times daily), and both drugs for 1 week, with each treatment period separated by a 1-week interval during which a placebo was given. Captopril significantly reduced blood pressure and plasma aldosterone, increased plasma renin activity (PRA), and did not change heart rate. Nifedipine exerted a similar effect on blood pressure and PRA, but it increased heart rate and did not change aldosterone. Captopril plus nifedipine further reduced blood pressure and increased PRA, did not change heart rate, and reduced aldosterone to values similar to those after captopril alone. The hypotensive effect of captopril was highly predictable by basal PRA values, and that of nifedipine by age, while PRA increments induced by captopril were unrelated to those induced by nifedipine. These data indicate that: 1) captopril and nifedipine exert an additive effect on blood pressure and renin; 2) captopril counteracts the heart rate increase induced by nifedipine; 3) nifedipine does not influence the aldosterone inhibition induced by captopril. It is suggested that the association of the two drugs can be usefully employed in the treatment of hypertension. (Hypertension 5 (supp III): III-154-III-156, 1983) KEY WORDS • hypertension • renin-aldosterone • calcium antagonists C APTOPRIL, an orally active inhibitor of angiotensin-converting enzyme, seems to exert its hemodynamic and humoral effect mainly by reducing angiotensin II formation.1 Since both vascular 2 and hormonal 2 " 4 actions of angiotensin il seem to be calcium-mediated, there is at least a theoretical basis for a possible interaction between captopril and nifedipine, a calcium channel inhibitor 3 with proved antihypertensive effect.6 Furthermore, besides any theoretical consideration, practical information could be derived on the usefulness of associating these two drugs in the treatment of hypertensive patients. MethodsNine outpatients, five men and four women aged 36 to 59 years, with mild to moderate uncomplicated essential hypertension, gave informed consent to the.From the Ospedale Umberto I, Siracusa, and the Clinica Medica I, University of Pisa, Pisa, Italy.Supported by Grant 82.02300.56 from CNR, Rome. Address for reprints: Dr. Antonio Salvetti, Clinica Medica I, University of Pisa, 56100, Pisa, Italy. study. After all drugs were discontinued for at least 3 weeks, patients received, according to a randomized sequence, captopril (25 mg t.i.d.), nifedipine (10 mg t.i.d.) and both drugs for 1 week, each active treatment period being preceded by 1 week of placebo administration. At the end of each period and at the same time of the day, 1 hour after the last dosing, body weight was measured, venous blood samples were obtained for measurement of plasma renin activity (PRA), sodium, potassium, and aldosterone, while blood pressure and heart rate were monitored every 10 minutes over a 2-hour period using...
The interaction of angiotensin converting enzyme (ACE) inhibition and atrial natriuretic factor (ANF) was investigated in six supine, sodium-replete, normal volunteers who received captopril (10 mg i.v. bolus followed by 10 mg/hr constant infusion) or vehicle superimposed on background 3-hour, constant, low-dose (1.5 pmol/kg/min) infusions of human ANF (99-126). Plasma converting enzyme activity was significantly inhibited but this had no effect on endogenous plasma ANF concentrations. ANF infusions, with or without captopril, caused similar increases in plasma ANF concentrations, and calculated metabolic clearance rates for ANF were unchanged. Similarly, blood pressure, heart rate, renal blood flow, glomerular filtration rate, and renal electrolyte excretion, including ANF-induced natriuresis, were unaffected by captopril. The combination of ANF plus captopril produced a significant increase in plasma aldosterone (79±8 vs. 60±6 pmol/1, p<0.05), cortisol (406±52 vs. 265±29 nmol/1, /><0.01), adrenaline (119±21 vs. 76±10 pg/ml, p<0.05), and noradrenaline (319±49 vs. 215±38 pg/ml, p<0.05) compared with tune-matched placebo data. Converting enzyme inhibition, in the absence of major changes in blood pressure or renal blood flow, has little effect on ANF metabolism or renal bioactivity. However, ACE inhibition and ANF combined may interact to increase activity of the hypothalamo-pituitary-adrenai axis and sympathetic nervous system by unknown mechanisms. (Hypertension 1989; 13:193-199) A trial natriuretic factor (ANF) with its diverse actions on renal and hemodynamic function and vasoactive hormone activity 1 continues to attract attention as a potentially major regulator of body fluid volume and arterial pressure. In many tissues ANF and the renin-angiotensin system appear to be counterbalanced.2 Angiotensin converting enzyme (ACE) inhibitors are now employed with increasing frequency in the treatment of both hypertension and heart failure. Recent trials demonstrate that ACE inhibitors improve survival in heart failure 3 and preserve renal function in diabetic patients. 4 Further major expansion in the use of these agents is likely. For these reasons, study of any possible interaction between ANF and ACE activity is relevant to the physiology of sodium balance and may have important clinical consequences.Already there is a body of circumstantial evidence pointing to an interaction between ACE inhibition
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