How do losartan and valsartan work?
Both losartan and valsartan are angiotensin II receptor blockers (ARBs) that treat high blood pressure by relaxing blood vessels. They block angiotensin II from binding to AT1 receptors, reducing blood pressure and easing heart workload. Losartan has a unique metabolite, EXP3174, which contributes about 40% of its activity and lasts longer than the parent drug.[1]
What conditions do they treat?
Losartan is FDA-approved for hypertension in adults and children over 6, diabetic nephropathy in type 2 diabetes, and stroke risk reduction in hypertensive patients with left ventricular hypertrophy. Valsartan treats hypertension (adults and children over 6), heart failure, post-heart attack survival improvement, and sometimes pediatric heart failure.[1][2]
How do dosing and half-life compare?
Losartan starts at 50 mg daily (max 100 mg), with a half-life of 2 hours (6-9 hours for metabolite). Valsartan starts at 80-160 mg daily (max 320 mg), with a 6-hour half-life. Both are once-daily, but valsartan's shorter effective duration may require consistent timing.[1][3]
What are the key side effects?
Common side effects overlap: dizziness, fatigue, high potassium. Losartan reports more upper respiratory infections and back pain; valsartan links to cough less often than ACE inhibitors but can cause diarrhea or fatigue. Both carry rare risks like angioedema or kidney issues. No head-to-head trials show major differences.[1][2][3]
Which is more potent or effective?
Valsartan is 10-20 times more potent by receptor affinity, allowing lower doses for similar effects. Meta-analyses show comparable blood pressure reductions (valsartan slightly better in some, losartan in others with hypertrophy). Choice depends on patient factors like kidney function.[3][4]
Cost and availability differences
Both are generic, so prices are low ($10-30/month). Losartan has more manufacturers; valsartan faced 2018-2019 recalls for NDMA carcinogen contamination, briefly tightening supply (resolved now).[5] No current shortages.
When would a doctor switch between them?
Switch if side effects occur (e.g., losartan for better metabolite coverage in liver issues; valsartan for heart failure). Both are first-line for hypertension per guidelines, with no superiority overall.[3]
[1]: FDA Label - Losartan
[2]: FDA Label - Valsartan
[3]: Drugs.com Comparison
[4]: PubMed - ARB Meta-Analysis
[5]: FDA Recall Info