A randomized and double-blind comparison of isradipine and spirapril as monotherapy and in combination on the decline in renal function in patients with chronic renal failure and hypertension.
AIMS: Treatment of hypertension in patients with chronic renal failure has been shown to postpone the decline in renal function. Treatment with an ACE inhibitor has been shown to be superior to conventional antihypertensive treatment, but it is not known how an ACE inhibitor compares to treatment with a calcium channel blocker or to treatment with a combination of these drugs. The aim of the study was to evaluate the rate of decline in GFR in patients with chronic renal failure and hypertension treated with isradipine and spirapril as monotherapy and in combination. METHODS: Sixty patients with chronic renal failure and hypertension were enrolled in the study. After enrollment, patients were followed prospectively for 6 months in the outpatient clinic on their usual antihypertensive medication, and then randomized to a double-blinded comparison of either spirapril 6 mg daily, isradipine 5 mg daily or spirapril 3 mg and isradipine 2.5 mg daily. After randomization, patients were followed for 21 months or until the need for dialysis. Every 3 months before and 3.5 months after randomization the glomerular filtration rate was measured by 51Cr-EDTA clearance and the effective renal plasma flow evaluated using the renal clearance of paraaminohippuric acid. RESULTS: Blood pressure and the decline in glomerular filtration rate did not differ between the groups before randomization. After randomization, the mean decline in the glomerular filtration rate was -0.32 ml/(min x month x 1.73 m2) in the spirapril group, -0.58 ml/(min x month x 1.73 m2) in the isradipine group and -0.14 ml/(min x month x 1.73 m2) in the combination group (p = 0.38). Twelve patients, 4 in each group, reached end-stage renal failure. No significant difference was found with respect to diastolic (p = 0.10) or systolic blood pressure (p = 0.08) during the treatment period, but a trend towards a better blood pressure control in the combination group was present. During treatment, the rate of decline in renal plasma flow did not differ significantly between the groups (p = 0.09), neither did the changes in filtration fraction (FF) (p = 0.58) nor the mean FF (p = 0.22) during the treatment. CONCLUSIONS: Our study indicated differences between the 3 treatment modalities in favor of combined therapy with respect to both the rate of decline in GFR and blood pressure control, but the differences where insignificant. Thus, the treatments might differ, but we were unable to confirm this because of large variation in GFR and small sample size.