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

OBJECTIVE: To assess the effectiveness of angiotensin converting enzyme inhibition in preventing the development of diabetic nephropathy (albuminuria greater than 300 mg/24h). 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/24h). 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 greater than 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 less than 0.05). Seven of the untreated patients progressed to diabetic nephropathy, whereas none of the captopril treated patients developed clinical overt diabetic nephropathy (p less than 0.05). Systemic blood pressure, glomerular filtration rate, haemoglobin A1c 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.