Drug interactions
Fludrocortisone + Metolazone
Severity: Major
Fludrocortisone and Metolazone: major interaction.
Last updated Sources: US FDA label
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Fludrocortisone has strong mineralocorticoid activity and, together with metolazone, markedly increases renal potassium loss. This raises the risk of significant hypokalaemia and arrhythmias.
What this interaction means in plain words
Fludrocortisone and Metolazone can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Fludrocortisone belongs to Endocrine; Metolazone belongs to Cardiovascular.
Why it happens
Additive kaliuresis: fludrocortisone stimulates mineralocorticoid receptors in the distal nephron while metolazone increases distal sodium delivery.
What to do
Monitor serum potassium and magnesium frequently, and supplement potassium or reduce doses as needed. Review the need for both drugs, particularly in patients with cardiac disease.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Metolazone
Other interactions of Fludrocortisone
Frequently asked questions
Can I take Fludrocortisone with Metolazone?
MediHelp rates the interaction as major. Fludrocortisone and Metolazone can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Fludrocortisone has strong mineralocorticoid activity and, together with metolazone, markedly increases renal potassium loss. This raises the risk of significant hypokalaemia and arrhythmias.
How serious is the interaction between Fludrocortisone and Metolazone?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor serum potassium and magnesium frequently, and supplement potassium or reduce doses as needed. Review the need for both drugs, particularly in patients with cardiac disease.
What other medicines interact with Metolazone?
MediHelp also lists interactions of Metolazone with, for example, Amifostine, Amlodipine-hydrochlorothiazide-valsartan, Amlodipine-olmesartan-hydrochlorothiazide. The full list is on the Metolazone page.
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