Combination antihypertensive therapy in the treatment of diabetic nephropathy

Diabetic nephropathy is one of the major causes of end-stage renal disease and is often associated with other macrovascular complications such as ischemic heart disease and peripheral vascular disease. Angiotensin converting enzyme inhibitors (ACE-I) and angiotensin II receptor blockers (AIIR) have both been shown to have a protective effect on the progression of diabetic nephropathy and have thus become the first choice for treatment of hypertension and/or renal involvement in patients with diabetes. However, most of these patients, especially those with type 2 diabetes, require two of more medications in order to reduce their blood pressure to the levels, which have been proposed in recently published consensus papers. These target blood pressure levels are 130/80 mm Hg in diabetic subjects with proteinuria of up to 1 g/day and 125/75 mm Hg in those with proteinuria in excess of 1 g/day. Combinations of different medications may have a synergistic effect. Some of the early studies using a combination of either a nondihydropyridine or a dihydropyridine calcium channel blocker with ACE-I demonstrated a synergistic effect on proteinuria in patients with diabetic nephropathy. However, these studies have not been substantiated, but calcium channel blockers, with their proven ability to reduce blood pressure, play an important role in the treatment of patients with diabetic nephropathy and hypertension. The combination of ACE-I with AIIR may have several theoretical advantages. Many studies using this combination have been performed in animal models of diabetes and in patients with diabetic and nondiabetic renal disease. Some of these studies have demonstrated a synergistic effect of the combination on proteinuria or hypertension, but the results have not been consistent in all studies. It may be concluded that, until additional studies provide more convincing evidence, this combination could be used in patients whose proteinuria or hypertension has not responded to either one of the agents as monotherapy or to a combination of other medications.