Do Not Add Losartan During Ongoing AKI
You should not initiate losartan in a patient with ongoing acute kidney injury. ARBs like losartan are recognized as potential nephrotoxins that must be avoided during AKI, as they directly compromise renal hemodynamics by blocking angiotensin II receptors, which decreases glomerular filtration pressure and can worsen already impaired kidney function 1, 2.
Why Losartan is Contraindicated in Active AKI
Hemodynamic Mechanism of Harm
- During AKI, renal function often depends on angiotensin II-mediated efferent arteriolar vasoconstriction to maintain glomerular filtration pressure 3
- Losartan blocks this compensatory mechanism, causing a critical fall in glomerular filtration pressure that can precipitate acute renal failure or worsen existing AKI 4, 5
- The FDA label explicitly warns that drugs inhibiting the renin-angiotensin system can cause changes in renal function including acute renal failure, particularly in patients whose renal function depends on RAS activity 3
High-Risk Clinical Scenarios
The FDA and consensus guidelines identify specific situations where losartan poses particular danger during AKI 1, 2, 3:
- Volume depletion (especially with concurrent diuretic therapy)
- Bilateral renal artery stenosis or unilateral stenosis in a solitary kidney
- Severe congestive heart failure
- Pre-existing chronic kidney disease
- Advanced age
Evidence of Harm
- Case reports document transient anuria lasting 8-10 hours after single doses of losartan in patients with activated renin-angiotensin systems 4
- Acute renal failure requiring hemodialysis has been reported with losartan use in vulnerable patients 5
- The NEPHRON-D trial demonstrated increased incidence of hyperkalemia and acute kidney injury with ARB use compared to monotherapy 3
Alternative Antihypertensive Options During AKI
Preferred Agents
Calcium channel blockers are the first-line alternative, as dihydropyridines like amlodipine have minimal effects on renal hemodynamics and can be safely used during AKI 2.
Loop diuretics (furosemide) are preferred in patients with volume overload and moderate-to-severe kidney dysfunction 2.
Beta-blockers can be used if concomitant ischemic heart disease or heart failure is present 2.
Thiazide-like diuretics may be considered only in mild-moderate AKI (eGFR >30 mL/min), though use with caution 2.
When to Consider Reintroducing Losartan After AKI Resolution
Timing and Prerequisites
Losartan should only be reintroduced after ALL of the following conditions are met 1, 2:
- GFR has stabilized (not just improved, but stable over time)
- Volume status is optimized
- Resolution of acute illness
- Mean arterial pressure >65 mmHg
- Serum potassium <5.5 mEq/L
Reintroduction Protocol
When restarting losartan after AKI recovery 2:
- Start with the lowest dose (25 mg daily)
- Monitor serum creatinine/eGFR and potassium within 1 week of restarting
- Accept a 10-20% increase in serum creatinine as tolerable
- Titrate slowly with monitoring every 1-2 weeks
- Continue annual monitoring during maintenance therapy
Long-Term Benefit After AKI Recovery
Importantly, observational data shows that continuing ARBs after complete AKI recovery is associated with reduced mortality and cardiovascular events without increased recurrent AKI risk 2. However, this benefit only applies after full recovery, not during ongoing AKI.
Critical Safety Monitoring
Absolute Contraindications During AKI
Never combine losartan with 2, 3:
- ACE inhibitors (substantially increased risk of hyperkalemia and acute kidney injury)
- Direct renin inhibitors like aliskiren
- Potassium supplements or potassium-sparing diuretics
Required Monitoring Parameters
If losartan must be used in high-risk situations after AKI resolution 1, 2:
- Check serum creatinine/eGFR within 1 week
- Check serum potassium within 1 week
- Monitor blood pressure for symptomatic hypotension
- Discontinue immediately if creatinine rises >20% or potassium >5.5 mEq/L