Few studies have directly compared the renoprotective effects of angiotensin II-receptor blockers and angiotensin-converting-enzyme (ACE) inhibitors in persons with type 2 diabetes. In this prospective, multicenter, double-blind, five-year study, we randomly assigned 250 subjects with type 2 diabetes and early nephropathy to receive either the angiotensin II-receptor blocker telmisartan (80 mg daily, in 120 subjects) or the ACE inhibitor enalapril (20 mg daily, in 130 subjects). The primary end point was the change in the glomerular filtration rate (determined by measuring the plasma clearance of iohexol) between the baseline value and the last available value during the five-year treatment period. Secondary end points included the annual changes in the glomerular filtration rate, serum creatinine level, urinary albumin excretion, and blood pressure; the rates of end-stage renal disease and cardiovascular events; and the rate of death from all causes. After five years, the change in the glomerular filtration rate was -17.5 ml per minute per 1.73 m2 (where the minus sign denotes a decrement) in the telmisartan-treated subjects, as compared with -15.0 ml per minute per 1.73 m2 in the enalapril-treated subjects; the treatment difference was thus -2.6 ml per minute per 1.73 m2 (95 percent confidence interval, -7.1 to 2.0 ml per minute per 1.73 m2)[corrected] The lower boundary of the confidence interval, in favor of enalapril, was greater than the predefined margin of -10.0 ml per minute per 1.73 m2, indicating that telmisartan was not inferior to enalapril. The effects of the two agents on the secondary end points were not significantly different after five years. Telmisartan is not inferior to enalapril in providing long-term renoprotection in persons with type 2 diabetes. These findings do not necessarily apply to persons with more advanced nephropathy, but they support the clinical equivalence of angiotensin II-receptor blockers and ACE inhibitors in persons with conditions that place them at high risk for cardiovascular events. Copyright 2004 Massachusetts Medical Society.
