ACEI and ARB reduce the rate of progression of chronic kidney disease (CKD) and reduce mortality. In fact, the NKF’s K/DOQI Clinical Practice Guidelines for Managing Hypertension and Antihypertensive Agents in CKD  (http://www.kidney.org/professionals/kdoqi/guidelines_bp/index.htm)
 recommend that most patients with CKD and hypertension be treated with either an ACEI or an ARB, combined with a diuretic. The effectiveness of ACEIs and ARBs is due to the capacity of these agents to lower blood pressure, glomerular hyperfiltration, and proteinuria. However, the agents remain underutilized, in part because of concerns that they may actually worsen kidney function.
 
An acute reduction in renal function (ARF) can occur when therapy is initiated or continued in four situations:
·        Blood pressure falls to low levels
·        Volume depletion from overaggressive diuretic therapy or non-renal losses is present
·        There is high-grade narrowing of the artery to both kidneys
·        Kidney blood flow is compromised by certain agents, particularly nonsteroidal anti-inflammatory agents (NSAIDs) or cyclosporine.
 
These situations must be anticipated before instituting therapy.  Even in the absence of these situations, an initial fall in GFR with ACEI/ARB therapy may occur and is an indication that the drugs are exerting their desired actions to help preserve kidney function.  A 10-20% increase in serum creatinine can be anticipated and is not an indication to discontinue the agents. However, unless one of the above situations exists, the decrease in GFR is usually less than 20%, is transient (occurring in the first two weeks of therapy), followed by stabilization or improvement. Thus, there is no serum creatinine level or GFR per se for which ACEI/ARB therapy is contraindicated.
 
High blood potassium levels (hyperkalemia) in advanced CKD are relatively common with ACEI/ARB therapy. This is more likely in diabetic patients with high blood sugars or in individuals on high potassium intakes, potassium-sparing diuretics, aldosterone antagonists, b-blockers or heparin. The routine use of potassium supplements or potassium-sparing agents should be discouraged in these patients.
 
Close monitoring of stage three-to-five CKD patients started on these agents is advisable. Serum creatinine (with calculated GFR http://www.kidney.org/professionals/kdoqi/gfr_page.cfm) and electrolytes should be evaluated before and again several weeks after beginning therapy.  If a significant change in serum creatinine has not been observed in the first month and blood pressure has been adequately controlled, the likelihood of ARF following this period is unlikely, unless
·        Diuretic dose is escalated
·        A NSAID is started or
·        Volume depletion develops from an intercurrent illness.
 
References
Bakris GL, Weir MR. Arch Int Med 160:685-693, 2000.
Schoolwerth AC, et al. Circulation 104:1985-1991, 2001.