The management of diabetic proteinuria. Which antihypertensive agent?

Diabetic renal disease is a clinical syndrome in which proteinuria is followed by the development of renal failure, and is commonly associated with the concomitant development of hypertension. In insulin-dependent diabetic (IDDM) patients, hypertension often first appears in the microalbuminuric phase of diabetic nephropathy whereas in non-insulin-dependent diabetic (NIDDM) patients, hypertension often antecedes nephropathy and may precede the diagnosis of diabetes. Antihypertensive regimens including diuretics, vasodilators such as hydralazine, beta-blockers and ACE inhibitors reduce proteinuria and delay the decline in renal function in IDDM patients with established nephropathy. No such data are as yet available for calcium antagonists. In microalbuminuric diabetic patients with hypertension, conventional antihypertensive agents, ACE inhibitors and calcium antagonists have been shown to decrease urinary albumin excretion. In the diabetic patient with normal blood pressure and microalbuminuria, there is much less information. It appears likely that ACE inhibitors reduce or retard the rate of increase in albuminuria in these patients. The effect on ultimately delaying or preventing renal failure remains unknown although the preliminary evidence is encouraging. Data on calcium antagonists remain inconclusive with some reports suggesting an increase in proteinuria with the dihydropyridine calcium antagonists. However, a recent longer term study suggested that nifedipine may prevent the rise in albuminuria which is generally observed in the untreated normotensive microalbuminuric subject.