Efficacy of captopril in postponing nephropathy in normotensive insulin dependent diabetic patients with microalbuminuria

Abstract

Objective: To assess the effectiveness of angiotensin converting enzyme inhibition in preventing the development of diabetic nephropathy (albuminuria >300 mg/24 h). Design: Open randomised controlled study of four years' duration. Setting: Outpatient diabetic clinic in tertiary referral centre. Patients: 44 normotensive (mean blood pressure 127/78 (SD 12/10) mm Hg) insulin dependent diabetic patients with persistent microalbuminuria (30-300 mg/24 h). Interventions: The treatment group (n = 21) was initially given captopril (25 mg/24 h). The dose was increased to 100 mg/24 h during the first 16 months and thiazide was added after 30 months. The remaining 23 patients were left untreated. Main outcome measures: Albuminuria, kidney function, development of diabetic nephropathy (albuminuria >300 mg/24 h), and arterial blood pressure. Results: Clinical and laboratory variables were comparable at baseline. Urinary excretion of albumin was gradually reduced from 82 (66-106) to 57 (39-85) mg/24 h (geometric mean (95% confidence interval)) in the captopril treated group, whereas an increase from 105 (77-153) to 166 (83-323) mg/24 h occurred in the control group (p < 0.05). Seven of the untreated patients progressed to diabetic nephropathy, whereas none of the captopril treated patients developed clinical overt diabetic nephropathy (p < 0.05). Systemic blood pressure, glomerular filtration rate, haemoglobin A(1c) concentration, and urinary excretion of sodium and urea remained practically unchanged in the two groups. Conclusions: The findings suggest that angiotensin converting enzyme inhibition postpones the development of clinical overt diabetic nephropathy in normotensive insulin dependent diabetic patients with persistent microalbuminuria.