Effects of an ACE inhibitor combined with a calcium channel blocker on progression of diabetic nephropathy

It is clear that angiotensin-converting enzyme (ACE) inhibitors slow progression of diabetic nephropathy to a greater extent than other antihypertensive agents when blood pressure (BP) is reduced to levels below 140/90 mm Hg. Recent studies also demonstrate that nondihydropyridine calcium channel blockers (NDCCBs) slow progression of diabetic nephropathy in people with pre-existing renal insufficiency secondary to non-insulin dependent diabetes mellitus. The combined effects of both a CCB and ACE inhibitor have recently been examined in both animal models of diabetes as well as patients with established diabetic nephropathy. These studies demonstrate the following points: (a) at comparable BP levels, a combination of an ACE inhibitor with a NDCCB result in a greater reduction in proteinuria when compared to either components alone; and (b) conversely, addition of an ACE inhibitor to a dihydropyridine CCB (DCCB) yields effects on proteinuria similar to the ACE inhibitor alone. Therefore, addition of an ACE inhibitor to a DCCB demonstrates protection against the effects of DCCB alone. Addition of an ACE inhibitor to a NDCCB does not potentiate the preservation of renal morphology associated with progression of diabetic nephropathy when compared to either of its components alone. Conversely, a DCCB/ACE inhibitor combination yields morphologic results similar to the ACE inhibitor alone. Taken together these results suggest that ACE inhibitors when combined with a NDCCB result in greater reductions in proteinuria, and similar preservation of renal morphology when compared to either of its components alone.