Hypertension is a common finding in
non-insulin-dependent diabetes mellitus (
NIDDM) nephropathy. African Americans have a high prevalence of
NIDDM and
hypertension, and are relatively resistant to the
antihypertensive effects of converting
enzyme inhibitors (CEI) but respond well to
calcium channel blockers (CCB). In the long-term study presented here, the effects of
isradipine, a
dihydropyridine calcium antagonist, on the course of the nephropathy were investigated and compared with the effects of
captopril in 31 African Americans with
NIDDM and
proteinuria (> or = 500 mg/day). The patients were stratified by levels of GFR and
proteinuria, and they were randomized to receive
isradipine (N = 16) or
captopril (N = 15); doses were adjusted to maintain similar BP levels (< 140/90). At 6 months, mean arterial pressure was similar (102 +/- 3 and 104 +/- 3 mm Hg in the
isradipine and
captopril groups, respectively) and GFR was unchanged (delta = -4 +/- 3 and +1 +/- 3 ml/min/1.73 in the
isradipine and
captopril groups, respectively; P = NS). However,
proteinuria in the
isradipine group increased by approximately 50% (2.01 +/- 0.40 versus 3.04 +/- 0.70 mg/mg
creatinine at baseline versus 6 months, respectively, P < 0.05), whereas
captopril reduced
proteinuria by 30% after 6 months (2.85 +/- 0.70 at baseline versus 2.30 +/- 0.70 mg/mg
creatinine, P < 0.05).
Dietary protein,
sodium intake, and HbA1C levels were similar in both groups and did not differ from baseline. It was concluded that over 6 months,
captopril reduces and
isradipine increases
proteinuria in African Americans with
NIDDM and nephropathy. Whether this contrasting effect on
proteinuria will result in different rates of progression is not known, but
dihydropyridine CCB should be used cautiously in African Americans with
diabetic nephropathy.