Comparison of the effects of captopril, diuretic and their combination in low- and normal-renin essential hypertension.

The purpose of this study was to compare the effects of captopril (CAP) and hydrochlorothiazide (HTZ), alone and in combination, on mean (+/- S.D.) blood pressure (BP), plasma renin activity (PRA), and plasma aldosterone concentration (PAC) in equal groups of six patients with low-renin and normal-renin essential hypertension. Renin classification was determined after furosemide (80 mg) stimulation; control measurements were made after each patient had been off all medications for at least 1 week. After a single 25 mg dose of CAP, BP decreased, PRA increased, and PAC decreased more (p less than 0.05) in the normal- than in the low-renin group. Each patient was then given the following in sequence for at least 2 weeks: CAP 25 mg t.i.d., HTZ 50 mg/day, and the combination. The results at the end of each treatment period indicated a modest, but significant reduction in blood pressure in both groups following CAP and HTZ; the effect of the combination was additive. Within each renin group under similar conditions there was no significant difference in mean PRA or PAC after each treatment. Thus, while the short-term effect of CAP on BP differed in patients with low- and normal-renin essential hypertension, the effect after chronic CAP was similar, comparable to that of HTZ and additive in combination in both groups.