Drug interactions
Chlorthalidone + Metolazone
Severity: Major
Chlorthalidone 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
Combining two thiazide-type diuretics produces sequential nephron blockade that markedly increases diuresis and loss of potassium, sodium and magnesium. This can cause severe hypokalemia, hyponatremia, volume depletion and renal impairment.
What this interaction means in plain words
Chlorthalidone 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.
Chlorthalidone belongs to Cardiovascular; Metolazone belongs to Cardiovascular.
Why it happens
Both inhibit the distal tubular Na+-Cl- cotransporter, producing additive natriuresis and kaliuresis.
What to do
Avoid duplicate thiazide-type therapy unless deliberately used for refractory edema under close supervision. Monitor electrolytes, renal function and weight frequently, and replace potassium and magnesium as needed.
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 Chlorthalidone
Other interactions of Metolazone
Frequently asked questions
Can I take Chlorthalidone with Metolazone?
MediHelp rates the interaction as major. Chlorthalidone 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. Combining two thiazide-type diuretics produces sequential nephron blockade that markedly increases diuresis and loss of potassium, sodium and magnesium. This can cause severe hypokalemia, hyponatremia, volume depletion and renal impairment.
How serious is the interaction between Chlorthalidone 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: Avoid duplicate thiazide-type therapy unless deliberately used for refractory edema under close supervision. Monitor electrolytes, renal function and weight frequently, and replace potassium and magnesium as needed.
What other medicines interact with Chlorthalidone?
MediHelp also lists interactions of Chlorthalidone with, for example, Amifostine, Atenolol-chlorthalidone, Candesartan-hydrochlorothiazide. The full list is on the Chlorthalidone page.
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