ModerateLoop diuretics×Potassium-sparing diuretics (mineralocorticoid receptor antagonists)
Updated · Methodology
Mechanism
Opposing effects on potassium: furosemide depletes it via the loop of Henle, spironolactone retains it by blocking aldosterone in collecting ducts. Target combination in heart failure, resistant hypertension, and ascites.
Symptoms
With a balanced combination, no specific symptoms. In chronic kidney disease, hyperkalaemia may occur: Weakness, fatigue, paraesthesias, arrhythmia. Symptoms develop at potassium above 5.5 mmol/L; life-threatening above 6.5 mmol/L.
Management
Check potassium and creatinine at 1 and 4 weeks after starting, then every 3 months. With creatinine clearance below 30 mL/min, do not prescribe spironolactone, or cap at 25 mg every other day. In dehydration, temporarily stop both until volume is restored.
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.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
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
- AEMPS: Ficha técnica: Espironolactona (nº registro 88191), sección 4.4 (2026)– AEMPS, CIMA, nº registro 88191, revisión 10/2026, sección 4.4