Major
Furosemide × Losartan
Loop diuretics×Angiotensin II receptor blockers (sartans)
Mechanism
Losartan (ARB) reduces aldosterone synthesis and angiotensin-dependent constriction of glomerular afferent arterioles. In a volume-depleted patient on a loop diuretic, the first losartan dose can sharply lower glomerular blood flow and trigger acute kidney injury.
Symptoms
Sharp blood pressure drop on the first dose: dizziness, syncope. Reduced urine output, rising creatinine. Weakness and paraesthesia from hyperkalaemia.
Management
The combination is standard in hypertension and heart failure. Before starting losartan, confirm there is no dehydration (after intensive diuretic therapy). Take the first dose in the evening, lying down. Check potassium and creatinine at 1 week.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Sources
- Lexicomp: Lexicomp Drug Interactions (2024)– Wolters Kluwer Clinical Drug Information, Inc. Lexi-Interact Online, 2024
- Pharmaceutical Press: Stockley's Drug Interactions, 12th edition (2024)– Preston CL (ed.). Stockley's Drug Interactions. 12th ed. London: Pharmaceutical Press; 2024