In a patient with estimated glomerular filtration rate <30 mL/min/1.73 m², should I initiate or continue an angiotensin‑converting‑enzyme inhibitor or the angiotensin‑II receptor blocker losartan, and what dosing and monitoring are recommended?

ACE Inhibitors and Losartan in eGFR <30: Continue with Dose Adjustment and Close Monitoring

Both ACE inhibitors and ARBs (including losartan) are strongly recommended to be continued—not discontinued—when eGFR falls below 30 mL/min/1.73 m², provided you initiate at reduced doses and implement rigorous monitoring for hyperkalemia and acute kidney injury. 1, 2, 3

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Primary Recommendation: Do Not Discontinue

• The American Diabetes Association explicitly states that renin-angiotensin system blockade should NOT be discontinued for minor increases in serum creatinine (<30%) in the absence of volume depletion, even when eGFR <30 mL/min/1.73 m². 1
• Continuation of ACE inhibitors or ARBs in patients with eGFR <30 mL/min/1.73 m² is associated with lower mortality and fewer major adverse cardiovascular events compared to discontinuation. 4
• KDOQI guidelines emphasize that RAAS antagonists provide nephroprotection and should not be routinely stopped when eGFR drops below 30 mL/min/1.73 m². 2

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Dosing Algorithm for eGFR <30 mL/min/1.73 m²

For ACE Inhibitors (e.g., Lisinopril):

• Start at half the usual recommended dose: 5 mg daily for hypertension or 2.5 mg daily for heart failure. 2, 5
• Maximum target dose after uptitration is 40 mg daily. 2, 5
• For patients with eGFR 10–30 mL/min/1.73 m² (including ~25 mL/min), FDA labeling mandates dose reduction to half the standard starting dose. 5

For Losartan:

• FDA labeling does NOT recommend losartan in patients with eGFR <30 mL/min/1.73 m², particularly in pediatric populations. 6
• However, the American Diabetes Association guidelines support ARB use (including losartan) in adults with eGFR <30 mL/min/1.73 m² when albuminuria or diabetic kidney disease is present, with close monitoring. 1
• If initiating losartan in this population, start at 25 mg daily (lower than the standard 50 mg dose) and uptitrate cautiously. 6

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Mandatory Monitoring Protocol

Initial Assessment (Within 1 Week):

• Check serum potassium and eGFR within 1 week of initiating therapy or any dose change. 2
• This early window is critical to detect hyperkalemia or acute worsening of renal function before irreversible harm occurs. 2

Follow-Up Schedule:

• Monitor potassium and eGFR monthly for the first 3 months. 2, 7
• After stabilization, check every 3 months indefinitely. 2, 3
• More frequent monitoring is required if adding other RAAS agents, diuretics, or during intercurrent illness. 7

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Hold or Discontinue Criteria

Temporarily Suspend ACE Inhibitor/ARB if:

• Serum potassium >5.5 mmol/L. 2
• eGFR declines >30% from baseline. 2
• Clinical evidence of acute kidney injury (e.g., rising creatinine, oliguria). 2
• During acute illness, bowel preparation, IV contrast administration, or major surgery. 2

Permanently Discontinue if:

• Serum potassium persistently >6.0 mmol/L despite intervention. 7
• Progressive decline in eGFR with clinical instability despite dose reduction. 2

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Concomitant Medication Management

Potassium Supplements:

• Discontinue or markedly reduce potassium supplements when ACE inhibitors or ARBs are used in eGFR <30 mL/min/1.73 m². 2, 7

Mineralocorticoid Receptor Antagonists (e.g., Spironolactone):

• Contraindicated when eGFR <30 mL/min/1.73 m² due to life-threatening hyperkalemia risk. 7
• If eGFR is 30–49 mL/min/1.73 m² and spironolactone is clinically indicated, use reduced dosing (12.5 mg every other day) only if potassium <5.0 mmol/L. 7

NSAIDs and Nephrotoxins:

• Avoid concomitant NSAIDs, aminoglycosides, and other nephrotoxic agents. 2

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ACE Inhibitor vs. Losartan: Which to Choose?

• Both ACE inhibitors and ARBs are equally recommended by the American Diabetes Association for patients with eGFR <60 mL/min/1.73 m² and albuminuria or diabetic kidney disease. 1
• ACE inhibitors have more robust FDA-approved dosing guidance for eGFR <30 mL/min/1.73 m², making them slightly easier to dose in this population. 5
• Losartan FDA labeling explicitly discourages use in pediatric patients with eGFR <30 mL/min/1.73 m², but adult use is supported by diabetes guidelines when albuminuria is present. 6, 1
• If the patient is already stable on either agent, continuation is preferred over switching, provided monitoring criteria are met. 1, 2

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Common Pitfalls to Avoid

Pitfall 1: Discontinuing therapy due to mild creatinine elevation

• A creatinine rise <30% is expected and acceptable when initiating RAAS blockade; do not stop therapy unless other red flags are present. 1

Pitfall 2: Failing to reduce starting dose

• Standard doses (e.g., lisinopril 10 mg or losartan 50 mg) are inappropriate in eGFR <30 mL/min/1.73 m²; always start at half-dose. 2, 5

Pitfall 3: Inadequate monitoring frequency

• Checking labs only at 3-month intervals is insufficient during initiation; the first week and monthly checks for 3 months are non-negotiable. 2

Pitfall 4: Continuing potassium supplements

• Hyperkalemia is the leading cause of RAAS blocker discontinuation in advanced CKD; proactively stop potassium supplementation. 2, 7

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Evidence Quality and Nuances

• The 2021 American Diabetes Association guidelines (Grade A evidence) provide the strongest support for continuing RAAS blockade in eGFR <30 mL/min/1.73 m² when albuminuria or diabetic kidney disease is present. 1
• A 2020 JAMA Internal Medicine propensity-matched cohort study of 3,909 patients demonstrated that discontinuing ACE inhibitors/ARBs after eGFR dropped below 30 mL/min/1.73 m² was associated with 39% higher mortality (HR 1.39,95% CI 1.20–1.60) and 37% higher risk of major adverse cardiovascular events (HR 1.37,95% CI 1.20–1.56), with no significant difference in end-stage kidney disease risk. 4
• FDA labeling for lisinopril explicitly provides dose-reduction guidance for eGFR 10–30 mL/min/1.73 m², whereas losartan labeling is less specific for this range. 5, 6
• The 2025 European Journal of Heart Failure consensus statement supports continuation of RAAS inhibitors in heart failure patients with eGFR <30 mL/min/1.73 m², emphasizing that discontinuation due to side effects (e.g., hyperkalemia) is associated with worse outcomes than managing the side effect itself. 1

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Practical Decision Algorithm

1. Confirm eGFR <30 mL/min/1.73 m² and assess for albuminuria, diabetic kidney disease, or heart failure. 1
2. If already on ACE inhibitor or ARB: Continue at current dose if stable; otherwise reduce to half-dose and monitor. 2
3. If initiating therapy: Start lisinopril 5 mg daily (or 2.5 mg if heart failure) OR losartan 25 mg daily. 2, 5, 6
4. Check potassium and eGFR within 1 week. 2
5. If potassium <5.5 mmol/L and eGFR decline <30%: Continue therapy and recheck monthly for 3 months. 2
6. If potassium 5.5–6.0 mmol/L: Hold dose, address contributing factors (e.g., stop potassium supplements, NSAIDs), and recheck in 3–5 days. 2, 7
7. If potassium >6.0 mmol/L or eGFR decline >30%: Discontinue therapy and consult nephrology. 2, 7
8. Uptitrate dose every 2–4 weeks as tolerated, not exceeding 40 mg daily for lisinopril or 100 mg daily for losartan. 2, 5, 6