Furosemide vs Spironolactone: side-by-side comparison
Furosemide (Loop diuretic) and Spironolactone (Potassium-sparing diuretic / aldosterone antagonist) belong to different therapeutic classes and are rarely substitutes for each other. The comparison is useful when a single patient is weighing both options for adjacent or overlapping needs.
| Property | Furosemide | Spironolactone |
|---|---|---|
| Therapeutic class | Loop diuretic | Potassium-sparing diuretic / aldosterone antagonist |
| CAS | 54-31-9 | 52-01-7 |
| ATC | C03CA01 | C03DA01 |
| Molecular weight | 330.7 g/mol | 416.57 g/mol |
| Brands with this active ingredient | 1 | 1 |
What they share
Furosemide and Spironolactone share the common regulatory framework for prescription active ingredients, bioequivalence standards for generics, and pharmacist oversight. Beyond that, points in common are limited.
Key differences
Furosemide acts by a different mechanism than Spironolactone, with indications that barely overlap. Comparing the two is useful when a clinician has mentioned both in the same context or the patient wants to understand why one was prescribed instead of the other.
Mechanisms compared
Furosemide: Furosemide acts on the thick ascending limb of the loop of Henle in the kidney, where it inhibits the Na+/K+/2Cl- co-transporter (NKCC2). Spironolactone: Spironolactone competitively blocks the mineralocorticoid (aldosterone) receptor in the distal tubule of the kidney, reducing sodium reabsorption and potassium excretion.
Indications compared
Furosemide: Furosemide is approved for the treatment of fluid overload due to heart failure, chronic kidney disease and liver cirrhosis (with or without ascites), as well as for acute pulmonary oedema. Spironolactone: Spironolactone is approved for heart failure with reduced ejection fraction, primary hyperaldosteronism, resistant hypertension, oedema in cirrhosis or nephrotic syndrome, and certain potassium-loss states.
Safety profile
Furosemide: Common adverse effects include electrolyte imbalances (low potassium, magnesium, sodium, calcium), volume depletion, dizziness on standing, and increased serum uric acid (with potential gout flares). Spironolactone: Common adverse effects include hyperkalaemia (especially with renal impairment or ACE inhibitors), gynaecomastia in men, menstrual irregularities in women, and dizziness from blood pressure effects.
Frequently asked questions
Is Furosemide better than Spironolactone? ▾
Furosemide and Spironolactone are not "better or worse" — they treat different things. The sensible question is which fits your specific need.
Can Furosemide and Spironolactone be combined? ▾
Whether they can be combined depends on the indications and the interaction profile of each. If both are in a single prescription, the prescriber has weighed it; in self-medication they should never be combined.
Do they have the same side-effect profile? ▾
No — they belong to different classes and have distinct side-effect profiles. Each has its own prescribing information.
Products with Furosemide
Products with Spironolactone
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.