The effect of captopril on renal hemodynamics in hypertensive patients

The effects of captopril (50 or 100 mg t.i.d.) with and without hydrochlorothiazide (25 or 50 mg/day) on renal blood flow, glomerular filtration rate, and the renin-angiotensin system were determined in 20 patients with mild to moderate essential hypertension. Normalization of blood pressure (supine diastolic blood pressure less than 90 mm Hg) was achieved in 12 patients after four or six weeks of captopril alone (147 +/- 3/100 +/- 3 mm Hg after a two-week placebo lead-in vs. 135 +/- 4/83 +/- 1 mm Hg after captopril, P less than 0.01/P less than 0.001). In these 12 patients, no significant alterations in renal blood flow or glomerular filtration rate were observed. Plasma renin activity increased two- to threefold above baseline levels, whereas serum and urinary aldosterone decreased by 23 and 35 per cent, respectively. Eight other patients remained hypertensive after four weeks of captopril alone (165 +/- 6/110 +/- 3 vs. 156 +/- 8/102 +/- 4 mmHg, P greater than 0.05/P less than 0.05). With addition of hydrochlorothiazide, blood pressure fell (P less than 0.001) to 129 +/- 7/84 +/- 3 mm Hg. Captopril alone or in combination with diuretic had no significant effect on renal hemodynamics. In the eight patients requiring diuretic, plasma renin activity remained constant after captopril monotherapy, but rose threefold after hydrochlorothiazide was added. The combination of these two antihypertensive agents significantly lowered serum aldosterone levels and urinary aldosterone excretion by 53 and 50 per cent, respectively. In summary, captopril with and without a thiazide diuretic reduced blood pressure without altering renal hemodynamics.