In insulin-dependent diabetes mellitus (IDDM), microalbuminuria predic
ts renal and cardiovascular disease. We report a combined analysis of
235 normotensive IDDM patients with microalbuminuria who participated
in two 24-month double-blind, randomised, placebo-controlled trials to
assess the effects of captopril 50 mg twice daily on the progression
to overt clinical albuminuria. Of the 225 patients who were evaluable
on an intent to treat basis, 25 of 114 placebo-treated patients (21.9%
) and 8 of 111 captopril-treated patients (7.2%) progressed to persist
ent clinical albuminuria. The risk of progression over 24 months was s
ignificantly reduced by captopril (p = 0.004) with a risk reduction of
69.2% (95% confidence interval (CI): 31.7 to 86.1%). This degree of r
isk reduction remained at the same level (62.9% [16.1-83.6%], p = 0.01
7) after adjustment for differences in time-varying mean arterial bloo
d pressure. Albumin excretion rate increased by an average of 14.2% [3
.1-26.5%] per year in the placebo-treated group compared with a reduct
ion of 9.6% [-18.6-0.4%] per year in the captopril-treated group (p =
0.002). The rate of fall of creatinine clearance tended to be faster i
n the placebo-treated group than in the captopril-treated group (-6.4
[-10.2--2.5] vs -1.4 [-5.3-2.6] ml . min(-1). 1.73 m(-2), p = 0.07). B
aseline albumin excretion rate (p < 0.0001) and glycated haemoglobin (
p = 0.03) were independent predictors of progression to clinical album
inuria and changes in mean arterial blood pressure (p = 0.02) and seru
m cholesterol level (p = 0.003) were significantly associated with per
centage changes in albumin excretion rate. Captopril reduces the risk
of progression to overt nephropathy in IDDM patients with microalbumin
uria, an effect partly independent of its blood pressure-lowering effe
cts.