Does losartan (angiotensin II receptor antagonist) affect kidney function?

Effects of Losartan on Kidney Function

Losartan has dual effects on kidney function - it provides renoprotective benefits in patients with albuminuria but can cause acute kidney dysfunction in certain high-risk populations. 1, 2

Renoprotective Effects

• Losartan improves kidney function by reducing intraglomerular pressure and proteinuria, which helps slow chronic kidney disease progression independent of its blood pressure-lowering effects 1
• In patients with type 2 diabetes and macroalbuminuria, losartan can reduce proteinuria by 20-35% within 3-6 months 1
• ARBs like losartan have demonstrated 100% improvement in urine albumin levels in patients with albuminuria, with benefits seen in both moderate and severe albuminuria 3
• Losartan may retard the progression of advanced renal insufficiency by slowing the decline in glomerular filtration rate, particularly in patients with decreased GFR at baseline 4

Risk of Kidney Dysfunction

• Losartan can cause changes in renal function including acute renal failure, particularly in patients whose renal function depends on the activity of the renin-angiotensin system 2
• High-risk populations include patients with renal artery stenosis, chronic kidney disease, severe heart failure, or volume depletion 2
• The FDA recommends monitoring renal function periodically in patients taking losartan, especially after initiation or dose increases 2
• Acute kidney failure has been reported in patients taking losartan even without predisposing factors such as renal artery stenosis 5

Hemodynamic Effects on Kidney Function

• Losartan causes efferent arteriolar vasodilation, which can lead to higher renal blood flow but may temporarily lower glomerular filtration rate 3
• This initial reduction in GFR is generally hemodynamic and not indicative of kidney injury unless persistent 1
• In patients with heart failure, kidney venous congestion rather than losartan use is often the major mechanism of worsening kidney function 3

Monitoring Recommendations

• Check serum creatinine and potassium within 2-4 weeks after initiation or dose increase of losartan 1
• Start at a lower dose in individuals with GFR <45 mL/min/1.73 m² 3
• Temporarily suspend losartan during interval illness, planned IV radiocontrast administration, bowel preparation for colonoscopy, or prior to major surgery 3
• Consider withholding or discontinuing therapy in patients who develop a clinically significant decrease in renal function 2

Special Considerations

• Avoid dual blockade of the renin-angiotensin system (combining losartan with ACE inhibitors or direct renin inhibitors) as this increases risks of hyperkalemia and acute kidney injury 2
• Monitor for hyperkalemia, especially in patients with advanced CKD, as losartan can increase serum potassium levels 2
• NSAIDs can attenuate the antihypertensive effect of losartan and may result in deterioration of renal function when used together 2

Clinical Application

• Losartan is recommended for patients with CKD and albuminuria, with or without diabetes, to reduce risk of kidney failure and cardiovascular events 1
• The beneficial effects of losartan on kidney function must be balanced against the risk of hyperkalemia and acute kidney injury 1
• Regular monitoring of kidney function is essential when using losartan, especially in high-risk populations 2