Effects of captopril, diuretic, and their combination in low-renin essential hypertension

Abstract

Six essential hypertensive patients aged 29 to 59 were selected for study because of low plasma renin activity (PRA). The purpose was to compare the changes in blood pressure (BP), PRA and plasma aldosterone concentration (PAC) before and after treatment with the angiotensin converting enzyme inhibitor, captopril (CAP), and the diuretic, hydrochlorothiazide (HTZ), alone and in combination. Control measurements were made after each patient had been off all medications for at least one week. Mean BP was significantly (P<0.05) reduced from control by acute and chronic CAP and HTZ; the effects were additive in combination. Neither PRA nor PAC changed significantly after any treatment; body weight and pulse rate also did not vary among the treatments. Thus, the acute response to CAP but not PRA was predictive of the eventual effect of CAP on BP in these patients. Since the effect of the treatments on BP could not be correlated with changes in PRA and PAC, additional mechanisms may be involved in the antihypertensive action of CAP in patients with low PRA.