Review: Renal protection by inhibition of the renin-angiotensin-aldosterone system

UNLABELLED: Renin-angiotensin-aldosterone system (RAAS) inhibition exerts a renoprotective effect independent of blood pressure reduction. Many studies using an end-point of proteinuria compared the effects of angiotensin-converting enzyme inhibitor (ACE-I) or angiotensin receptor blocker (ARB) monotherapy with combination ACE-I/ARB therapy. Despite methodological limitations, most studies suggest that combination therapy provides a greater antiproteinuric effect than monotherapy, perhaps because of more prolonged and complete RAAS inhibition. COOPERATE and ONTARGET used more robust end-points to study renoprotective effects. In COOPERATE, combination therapy resulted in significantly longer times to doubling serum creatinine or developing end-stage renal disease than trandolapril or losartan monotherapy. However, a secondary ONTARGET finding was that combination therapy significantly increased the risk for renal dysfunction compared with ramipril or telmisartan alone. Eventually, the VA NEPHRON-D trial should provide definitive data relating to patients with diabetic nephropathy. RESULTS: of AVOID suggest the renoprotective benefits of combination therapy extend to the direct renin inhibitors (DRI). In AVOID, combination therapy with aliskiren, a DRI, and losartan resulted in 20% greater protein excretion decrement than losartan monotherapy. Future trials should examine higher RAAS inhibitor doses, facilitate differentiation of renoprotective and antihypertensive effects of RAAS blockade, and use end-points that robustly demonstrate renoprotective effects.