Treatment of diabetic nephropathy with angiotensin II receptor antagonist.

Type 2 diabetes is an ever-growing problem worldwide. Approximately 40% of the patients with type 2 diabetes will develop diabetic kidney disease. In the United States, diabetes has become the most common single cause of endstage renal disease defined by the need for dialysis or transplantation. Patients with type 2 diabetes and diabetic nephropathy have a dramatically increased cardiovascular risk. The Irbesartan Diabetic Nephropathy Trial was designed to determine whether the use of irbesartan or a calcium channel blocker would provide protection against the progression of nephropathy due to type 2 diabetes beyond that attributable to the lowering of blood pressure. In that study, 1715 hypertensive patients with nephropathy due to type 2 diabetes were randomly assigned to irbesartan 300 mg/day or amlodipine 10 mg/day, or placebo. All patients randomized in this trial had more than 900 mg of protein in their urine and serum creatinines between 1.0 mg/dl and 3.0 mg/dl. The target blood pressure was 135/85 mmHg or less in all groups. The primary outcome was time to a combined endpoint of doubling of their baseline serum creatinine concentration, the development of endstage renal disease, or death from any cause. The mean duration of follow-up was 2.6 years. Treatment with irbesartan was associated with a risk of the primary composite endpoint that was 20% lower than that in the placebo group (P = 0.02) and 23% lower than that in the amlodipine group (P = 0.006). The risk of doubling of the serum creatinine concentration was 33% lower in the irbesartan group than in the placebo group (P = 0.003) and 37% lower in the irbesartan group than in the amlodipine group (P < 0.001). Treatment with irbesartan was associated with a relative risk of endstage renal disease that was 23% lower than that in both other groups. These differences were not accounted for by differences in the blood pressures that were achieved. Proteinuria was reduced on average by 33% in the irbesartan group as compared with 6% in the amlodipine group and 10% in the placebo group. The angiotensin II receptor blocker irbesartan was shown to be effective in protecting against the progression of nephropathy due to type 2 diabetes. In a study done in patients with type 2 diabetes and early nephropathy as manifested by microalbuminuria, 590 hypertensive patients with type 2 diabetes and microalbuminuria were randomized to receive either irbesartan 150 mg/day or irbesartan 300 mg/day and followed for 2 years. The primary outcome in that trial was the time to the onset of diabetic nephropathy, defined by persistent albuminuria in overnight specimens, with a urinary albumin excretion rate that was more than 200 mg/min or at least 30% higher than the baseline level. The irbesartan 150 mg/day group demonstrated a 39% relative risk reduction versus the control group in the development of overt proteinuria. The irbesartan 300 mg/day group demonstrated a highly significant 70% risk reduction versus the control group (P < 0.001). The albumin excretion rate was reduced in the two irbesartan groups throughout the study (−11% and −38% at 24 months compared with baseline in the irbesartan 150-mg and 300-mg groups, respectively). The albumin excretion rate remained unchanged in the control group. Irbesartan was demonstrated in the above study to be renoprotective, independent of its blood pressure-lowering effect, in patients with type 2 diabetes and microalbuminuria. Thus, irbesartan, an angiotensin receptor blocker, was demonstrated to be significantly renoprotective in patients with type 2 diabetes with either early nephropathy (microalbuminuria) or late nephropathy (proteinuria). The renoprotective effects of irbesartan were above and beyond the effects irbesartan had on systemic blood pressure. Patients with type 2 diabetes and either early or late diabetic nephropathy should be treated with the angiotensin II receptor blocker irbesartan.