Spironolactone and Fludrocortisone Acetate: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Spironolactone
Fludrocortisone Acetate
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
A paradoxical dose-related increase in urinary potassium excretion
Interaction Deep Dive
Coadministration of canrenoate potassium or spironolactone with fludrocortisone may result in a paradoxical dose-related increase in urinary potassium excretion1.
Why it happens (mechanism)
Urinary potassium excretion related to increased urine volume
Literature reports
1 report — tap to read
a) In 12 healthy subjects (19 to 33 years old) treated with fludrocortisone 1.5 mg daily, treatment with canrenoate potassium 100 mg, 150 mg, or 200 mg or with spironolactone 25 mg, 50 mg, or 100 mg, showed a significant (p less than 0.05) dose-related increase in potassium excretion after 12 to 16 hours attributed to increased urine flow rate 1.
Common questions
Can I take Spironolactone and Fludrocortisone Acetate together?
A paradoxical dose-related increase in urinary potassium excretion Always confirm with your pharmacist or prescriber before making any change.
How serious is the Spironolactone and Fludrocortisone Acetate interaction?
It is rated minor. Usually limited clinical impact.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Spironolactone or Fludrocortisone Acetate need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (1)
- Ramsay LE, Harrison IR, Shelton JR, et al: Paradoxical potassium excretion in response to aldosterone antagonists. Eur J Clin Pharmacol 1977; 11:101-105. PubMed
Keep reading about Spironolactone
Keep reading about Fludrocortisone Acetate
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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