Contrasting effects of enalapril and metoprolol on proteinuria in diabetic nephropathy.

OBJECTIVE: To assess whether angiotensin converting enzyme inhibition reduces proteinuria in diabetic nephropathy more than blood pressure reduction with other antihypertensive treatment. DESIGN: Prospective, open randomised study lasting eight weeks in patients with diabetic nephropathy. SETTING: Outpatient nephrology clinics. PATIENTS: 40 Patients with type I diabetes and diabetic nephropathy with reduced renal function. INTERVENTION: Antihypertensive treatment with enalapril or metoprolol, usually combined with frusemide. MAIN OUTCOME MEASURES: Arterial blood pressure and urinary excretion of albumin and protein. RESULTS: Arterial blood pressure after eight weeks was 135/82 (SD 13/7) mm Hg in the group given enalapril and 136/86 (16/12) mm Hg in the group given metoprolol. Proteinuria and albuminuria were similar in both groups before randomisation. After eight weeks' treatment, the geometric mean albumin excretion was 0.7 (95% confidence interval 0.5 to 1.2) g/24 h in the patients given enalapril and 1.6 (1.1 to 2.5) g/24 h in the patients given metoprolol (p less than 0.02). The proteinuria was 1.1 (0.7 to 1.7) and 2.4 (1.6 to 3.6) g/24 h respectively (p less than 0.02). CONCLUSIONS: Antihypertensive treatment with enalapril reduced proteinuria in patients with diabetic nephropathy more than an equally effective antihypertensive treatment with metoprolol. This points to a specific antiproteinuric effect of the angiotensin converting enzyme inhibitor independent of the effect on systemic blood pressure.