Use of MRBs in Patients with CKD Although some doubt remains about whether ACE inhibitors and ARBs are superior to other blood pressure lowering drugs in slowing the progression of CKD, they may provide marginal extra benefit and are widely recommended in national and international guidelines. Conversely, the traditional approach by nephrologists to MRB drugs has been to avoid their use because of the risk of azotaemia and hyperkalaemia. There are both theoretical and empirical reasons why this avoidance may be incorrect. Firstly, CKD is characterised by an abnormal combination of chronic sodium overload and high (unsuppressed) levels of circulating aldosterone; the normal relationship between circulating volume and aldosterone secretion appears to be altered (aldosterone escape). Secondly, in a large proportion of patients with CKD on standard treatment with ACE inhibitors or ARBs, there is aldosterone 'breakthrough' so that aldosterone levels are high despite inhibition of the system by prevention of angiotensin II formation or inhibition of angiotensin receptors. Thus patients with CKD are exposed to high levels of aldosterone despite standard treatment. The only other common disease state in which high aldosterone production continues to occur in the face of sodium overload is chronic heart failure in which MRB therapy is of major prognostic benefit reducing both adverse cardiovascular events and total mortality.