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Metolazone

ATC code C03BA08

Also known as: Metolazon

Key facts
Active substance
Metolazone
Drug class
Diuretic
ATC code
C03BA08
Authorisation
authorised nationally; no central EU authorisation
Information as of
2026-10-29

Key facts

Metolazone is, per the US prescribing information, a quinazoline diuretic with thiazide-like properties used to treat edema in heart and kidney disease and hypertension.

What it is used for

  • Salt and water retention, including edema accompanying congestive heart failure.
  • Edema accompanying renal diseases, including nephrotic syndrome and diminished renal function.
  • Hypertension, alone or with antihypertensive drugs of a different class.

Dosing

  • Single daily dose; titrate individually by indication and response to the minimal dose that maintains the desired effect.
  • Edema of cardiac failure or renal disease: 5 to 20 mg once daily.
  • Mild to moderate essential hypertension: 2½ to 5 mg once daily; the blood pressure effect may take three or four days to three to six weeks.
  • Metolazone tablets are not interchangeable with more rapidly available formulations (MYKROX); switching requires new titration – see the full text.
  • Use caution in severely impaired renal function (accumulation may occur).

Contraindications

  • Anuria.
  • Hepatic coma or precoma.
  • Known allergy or hypersensitivity to metolazone.

Important warnings

  • Do not interchange: metolazone tablets with slow and incomplete bioavailability are not therapeutically equivalent at the same doses to MYKROX.
  • Rare rapid onset of severe hyponatremia and/or hypokalemia after initial doses; stop immediately if this occurs.
  • Hypokalemia with weakness, cramps and cardiac dysrhythmias; check potassium regularly, especially with digitalis.
  • Use with furosemide can cause unusually large or prolonged losses of fluid and electrolytes.
  • Hyperuricemia or gout, hyperglycemia, azotemia, hypercalcemia, orthostatic hypotension; cross-allergy with sulfonamides and thiazides.

Side effects

  • Usually well tolerated, with mostly mild and transient adverse reactions; no frequencies are given.
  • Cardiovascular: chest pain, orthostatic hypotension, excessive volume depletion, venous thrombosis, palpitations.
  • Nervous system: syncope, dizziness, lightheadedness, fatigue, weakness, headache.
  • Skin and digestive: toxic epidermal necrolysis, Stevens-Johnson syndrome, photosensitivity, hepatitis, pancreatitis, nausea, vomiting.

Interactions

  • Lithium: diuretics should generally not be given together (high risk of lithium toxicity).
  • Furosemide and probably other loop diuretics: unusually large or prolonged fluid and electrolyte losses.
  • Digitalis glycosides: diuretic-induced hypokalemia can lead to serious arrhythmias.
  • Other antihypertensives, alcohol, barbiturates and narcotics add to the hypotensive effect.

Pregnancy and breastfeeding

  • Routine use of diuretics in an otherwise healthy pregnant woman is inappropriate.
  • Metolazone appears in breast milk.

Summary of the official product information, written with AI on 2026-10-29. Every number was checked automatically against the original text. Not reviewed by a physician – the full official text is authoritative.

Full official text →

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For patients

Patient information (US)

This product has no separate US patient information.

Authorisation and brand names by country

Medicines with exactly this active-substance composition, as listed in the national registers – alphabetical and without ranking. Whether a product is currently available is not shown here.

Brand names in 7 more European countries
Denmark
Metolazon Abcur
Finland
Metolazon Abcur
Iceland
Metolazon Abcur
Italy
Zaroxolyn
Norway
Metolazon Abcur
Portugal
Diulo
Sweden
Metolazon Abcur

EMA – Article 57 product data (EU/EEA), 2026-10-29

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Sources

  1. U.S. Food and Drug Administration. Metolazone (Amici Pharma, Inc) – Prescribing Information, 2026-04-01. DailyMed (NLM), 2026-10-29. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=cbfa3d5c-cce9-4afa-b064-06f1e1041eac
  2. Wikidata (CC0): ATC C03BA.

Editorial: Medelix editorial team · last updated 2026-10-29 · How these pages are made · Report an error

Source: U.S. Food and Drug Administration (FDA), prescribing information, via DailyMed (NLM); public domain. Not advertising, not a treatment recommendation. For questions about your own treatment, ask your doctor or pharmacist.