- pre-existing chronic kidney disease - new use of or change in dose of ace-inhibitors or angiotensin receptor blocker (arb) within the last 6 months - acute kidney injury at the time of enrollment defined as either increase pf serum creatinine by more than 50% or 0.3 mg/dl above baseline or estimated creatinine clearance (by mdrd) of less than 60 ml/min (if no baseline serum creatinine available) - pregnant and breastfeeding women - contraindicated medications: new use or change of medications from start of trial (start of an ace inhibitor or arb within 6 months of trial).

- pre-existing chronic kidney disease - new use of or change in dose of ace-inhibitors or angiotensin receptor blocker (arb) within the last 6 months - acute kidney injury at the time of enrollment defined as either increase pf serum creatinine by more than 50% or 0.3 mg/dl above baseline or estimated creatinine clearance (by mdrd) of less than 60 ml/min (if no baseline serum creatinine available) - pregnant and breastfeeding women - contraindicated medications: new use or change of medications from start of trial (start of an ace inhibitor or arb within 6 months of trial).