The effects of amlodipine and enalapril on renal function in adults with hypertension and nondiabetic nephropathies: a 3-year, randomized, multicenter, double-blind, placebo-controlled study.

BACKGROUND

Placebo-controlled trials have found that angiotensin-converting enzyme inhibitors (ACEIs) decrease proteinuria and slow the progression of nondiabetic nephropathies. However, head-to-head comparisons of ACEIs and calcium channel blockers (CCBs) have shown conflicting results. Indeed, a recent metaanalysis concluded that there is still uncertainty about the greater renoprotection seen with ACEIs or angiotensin II receptor blockers in nondiabetic patients with renal disease, particularly when using true glomerular filtration rate (GFR) as the primary outcome.

OBJECTIVE

The objective of this 3-year, randomized, multicenter, double-blind, placebo-controlled study was to compare true GFR decline (measured by yearly 51Cr-EDTA blood clearance) in nondiabetic, nonnephrotic adult hypertensive patients with estimated creatinine clearance of 20 to 60 mL/min.1.73 m(2), when randomized to a CCB (amlodipine, 5-10 mg/d) or an ACEI (enalapril, 5-20 mg/d).

METHODS

Patients (aged 18-80 years) entered a 4-week placebo run-in washout period and previous antihypertensive drugs were tapered off over 2 weeks. Add-on treatments were atenolol (50-100 mg/d), loop diuretics (furosemide, 20-500 mg/d or torsemide, 5-200 mg/d), alpha-blockers (prazosin, 2.5-5 mg/d or doxazosin, 1-16 mg/d), and centrally acting drugs (rilmenidine, 1-2 mg/d or methyldopa, 250-500 mg/d). The primary end point was true GFR measured by yearly (51)Cr-EDTA blood clearance. Secondary end points included a clinical composite of renal events and tolerability collected by a full clinical and laboratory evaluation at each study visit. Post hoc analyses for the change in GFR, proteinuria, and time to clinical events were also planned on baseline proteinuria subgroups (<1 and >or=1 g/d) before unblinding the database.

RESULTS

Three hundred eighteen patients entered the run-in period and 263 patients (156 men/107 women; mean age, 58 years) were randomized to receive either amlodipine (5 mg/d, n=132) or enalapril (5 mg/d, n=131). Blood pressure declined from 165/102 mm Hg to 138/84 mm Hg and 138/85 mm Hg with amlodipine and enalapril, respectively (no between-group significance). Only 20.8% of the patients randomized to ACEI treatment received diuretics at the last observation. No statistically significant difference was found between amlodipine and enalapril in GFR decline (-4.92 and -3.98 mL/min.1.73 m(2), respectively, at last observation) and composite secondary end point after a median follow-up of 2.9 years, including in the subgroup of patients with proteinuria >1 g/d at baseline. Protein excretion rate decreased significantly from baseline in patients taking enalapril plus diuretics (median -270 mg/d; P<0.001) but not in patients taking amlodipine plus diuretics (-25 mg/d at last observation).

CONCLUSION

In this cohort of nondiabetic, nonnephrotic hypertensive patients, no statistically significant difference in true GFR decline was found over 3 years between amlodipine-treated patients and enalapril-treated patients with main add-on treatment with ss-blockers, including in the subgroup of patients with proteinuria >1 g/d.