Drug interactions
Furosemide + Metolazone
Severity: Major
Furosemide 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
Metolazone potentiates furosemide by blocking compensatory distal sodium reabsorption, producing strong diuresis. This can cause severe hypokalemia, hyponatremia, hypomagnesemia, dehydration and kidney injury.
What this interaction means in plain words
Furosemide 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.
Furosemide belongs to Cardiovascular; Metolazone belongs to Cardiovascular.
Why it happens
Sequential nephron blockade at the loop of Henle and distal convoluted tubule gives synergistic natriuresis and potassium loss.
What to do
Use a low metolazone dose for a limited period and monitor weight, urine output, sodium, potassium, magnesium and creatinine within the first days. Replace electrolytes promptly and reduce doses if over-diuresis occurs.
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 Furosemide
- Amifostine + Furosemide Major
- Amikacin + Furosemide Major
- Carbenoxolone + Furosemide Major
- Cephaloridine + Furosemide Major
- Cisplatin + Furosemide Major
- Digoxin + Furosemide Major
Frequently asked questions
Can I take Furosemide with Metolazone?
MediHelp rates the interaction as major. Furosemide 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. Metolazone potentiates furosemide by blocking compensatory distal sodium reabsorption, producing strong diuresis. This can cause severe hypokalemia, hyponatremia, hypomagnesemia, dehydration and kidney injury.
How serious is the interaction between Furosemide 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: Use a low metolazone dose for a limited period and monitor weight, urine output, sodium, potassium, magnesium and creatinine within the first days. Replace electrolytes promptly and reduce doses if over-diuresis occurs.
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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