Renin-angiotensin-aldosterone system blockade and renal protection: angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers?

Renal function is closely associated with cardiovascular risk, to the extent that even minor renal abnormalities, which are present in 10% of the general population, carry a greatly elevated risk of cardiovascular disease, target-organ damage and death. Reducing blood pressure by 20 mmHg or more in patients with severe hypertension (>160/100 mmHg) and advanced renal disease is sufficient to ensure a considerable reduction in proteinuria. In patients with less severe disease, however, blockade of the renin-angiotensin-aldosterone system (RAAS) is necessary to restore normal renal function. Clinical studies have shown that angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs), which both overcome the activity of angiotensin II, provide renoprotection in diabetics and non-diabetic populations. Which class of drugs is more effective remains a subject of debate, but the evidence favours ARBs for providing more effective renoprotection in patients at risk of diabetic nephropathy. The ARBs preserve renal haemodynamics and reduce progression to end-stage renal disease by around 25% in patients with overt nephropathy and prevent progression to overt disease by up to 70% in patients with mild renal impairment. The combination of ARBs and ACE inhibitors is even more protective, halving the number of patients with progression of renal impairment compared with either monotherapy. Long-term clinical studies now under way will help to establish the relative efficacies of the ARBs and ACE inhibitors and provide greater insight into the benefits of combination therapy.