Although calcium antagonists have long been introduced into antihypertensive treatment, little is known of their renal long-term action in patients with diabetes mellitus, diabetic nephropathy, or hypertension. Much of the current information concerning this issue is from short-term studies. While urinary albumin excretion, a major indicator of glomerular damage in patients with diabetes mellitus, remains unchanged or even increases during short-term calcium antagonist treatment in type 1 diabetic patients, it is mostly reduced in type 2 diabetic patients, especially by diltiazem and nicardipine. There have been discrepant observations in studies lasting 6-months or longer. In many of the studies, urinary albumin excretion is not decreased by calcium antagonist treatment, although blood pressure is well controlled. Albuminuria is markedly reduced, however, after nitrendipine or diltiazem treatment. While calcium antagonists such as diltiazem, nicardipine, or nitrendipine may be as efficacious as converting enzyme inhibitors in preventing the progression of diabetic kidney disease in diabetic patients, the beneficial efficacy of others is less apparent. Reduced albuminuria may be more difficult to attain in macroalbuminuric patients with advanced nephropathy. However, considerations on the potential effects of calcium antagonist long-term treatment on cardiovascular morbidity or mortality in diabetic patients should not be overlooked when their renal action is under discussion. Thus, further studies are needed to define the role of calcium antagonists more precisely in the long-term treatment of diabetic patients with hypertension or diabetic nephropathy.
