Antihypertensive and Renal Effects of Isradipine in Essential Hypertension: Focus on Renin System Activity

Abstract

Calcium antagonists are known to exert various effects on the kidney that might modulate their antihypertensive potential. This study evaluated the renal effects, along with the efficacy, of isradipine in two subgroups of patients with mild to moderate essential hyper tension (EH), defined according to plasma renin activity (PRA). Twenty-six patients were randomly assigned to receive 12-week treatment with slow-release isradipine (2.5-5 mg) or placebo. Assessment of PRA related to concurrent 24-hour sodium excretion was used to define patients with high/medium (n=16) and low renin profile (n=10). Urinary albumin excretion (UAE), serum creatinine and glomerular filtration rate (GFR, as endogenous creatinine clearance) were measured. Blood pressure (BP) decrease with isradipine was greater in the low PRA group as compared with the high/medium PRA group (P<0.05), and normalization of BP was achieved in all low-renin patients compared with 57% in the high/medium PRA group. BP reduction in the placebo group was statistically not significant. Isradipine, but not placebo, induced significant reduction in UAE (P<0.05); the decrease was similar in both PRA groups. Treatment did not cause any significant changes in GFR, PRA, urinary sodium or creatinine excretion, or serum aldosterone or creatinine concentrations. The decrease of BP in the whole isradipine- treated group was inversely correlated with pretreatment serum creatinine as well as with basal urinary creatinine excretion. In conclusion, the antihypertensive effect of isradipine was more pronounced in low-renin EH patients, despite similar effects on renal function and UAE in both PRA groups.