Effect of captopril on heavy proteinuria in azotemic diabetics.

We investigated whether captopril, an angiotensin-converting-enzyme inhibitor, would reduce proteinuria in patients with advanced diabetic nephropathy. Captopril (37.5 mg given in divided doses three times daily) was administered to 10 azotemic diabetics with heavy proteinuria. Urinary protein decreased promptly within two weeks (from 10.6 +/- 2.2 to 6.1 +/- 1.4 g per day [mean +/- S.E.M.]; P less than 0.01). The decrease in proteinuria did not coincide with a fall in systemic blood pressure or in the blood glucose concentration. Serum creatinine and potassium values did not change in any of the patients except one. We suggest that captopril caused a decrease in intrarenal hypertension, which contributed to the reduction of urinary protein excretion. The therapeutic value of this intervention remains to be established.