Renal protection by angiotensin II receptor antagonists in patients with type 2 diabetes

To the Editor: A recent editorial in the Journal attempted to define a role for angiotensin II receptor (AIIR) antagonists in patients with type 2 diabetes.1 This was in the light of recent trial evidence that these agents reduce progression to renal failure in patients with type 2 diabetes and diabetic renal disease. Unfortunately, the guidelines provided were somewhat confusing and fragmented. I believe that a simpler treatment guide can be constructed, particularly when it is emphasised that the aim in diabetes is to use agents that prevent not only renal failure but also cardiovascular events.

Substantial evidence already supports a role for the angiotensin-converting enzyme (ACE) inhibitor ramipril in treatment of diabetes. The HOPE study included 3577 people with diabetes and another risk factor for cardiovascular disease who were randomised to either placebo or ramipril (10 mg) for 4.5 years.2 This group had a mean baseline blood pressure of 142/80 mmHg and no clinical proteinuria. Ramipril lowered the risk of the combined primary outcome of myocardial infarction, stroke and cardiovascular death by 25% (P ≤ 0.001), and this effect was independent of blood-pressure lowering. Furthermore, ramipril reduced progression to overt nephropathy by 22%, with a reduction evident in patients with or without proteinuria.2

This protective effect of ramipril on renal function is consistent with previous evidence that ACE inhibitors slow progression of chronic renal failure in diabetes,3,4 and that ramipril slows progression of chronic renal failure in non-diabetic nephropathy.5

Whether other ACE inhibitors have the same effect as ramipril on cardiovascular events, and what doses obtain such an effect, remains speculative. Similarly, while there is now evidence that AIIR antagonists also have renal-protective effects, there is no definitive evidence that they protect against cardiovascular events.

In view of this, and in the absence of comparative trials, ramipril (and not other ACE inhibitors or AIIR antagonists) is currently the first choice for treatment for diabetic patients with hypertension, with normotension and microalbuminuria, or with hypertension and micro- or macroalbuminuria. As most patients with diabetes and hypertension require multiple agents to achieve a target blood pressure less than 130/80 mmHg, additional therapy with a β-blocker, diuretic or calcium-channel blocker is often necessary.

The significance of the newly available trial data is that AIIR antagonists provide an alternative to ramipril for reducing progression to chronic renal failure in patients with diabetic nephropathy who cannot tolerate ACE inhibitors because of the side effect of cough.