Reviewed on 8/10/2021

What Is Metolazone and How Does It Work?

Metolazone is a prescription drug and is a "water pill" (diuretic) that increases the amount of urine you make, which causes your body to get rid of excess water. This drug is used to treat high blood pressure. Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems.

Metolazone also reduces swelling/fluid retention (edema) which can result from conditions such as congestive heart failure or kidney disease. This can help to improve symptoms such as trouble breathing.

Metolazone is available under the following different brand names: Zaroxolyn.

What Are Dosages of Metolazone?

Dosages of Metolazone:

Adult and pediatric dosages:

  • 2.5 mg (geriatric only)
  • 5 mg
  • 10 mg

Dosage Considerations – Should be Given as Follows:


  • 2.5-5 mg orally once daily; may be increased to 20 mg once daily as needed

Edema in Adults

  • 2.5-10 mg orally once daily initially; may be gradually increased to 20 mg once daily


  • 2.5 mg orally once daily or every other day

Pediatric (off-label)

  • 0.2-0.4 mg/kg/day orally in single dose or divided every 12 hours

Dosing Modifications

Dosing Considerations


  • Increased risk of azotemia and electrolyte depletion when used in combination with diuretics in elderly

Overdose Management


Kidney Stones: Symptoms, Causes, and Treatment See Slideshow

What Are Side Effects Associated with Using Metolazone?

Side effects of metolazone include:

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Metolazone?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first.

Metolazone has no known severe interactions with other drugs.

Serious Interactions of metolazone include:

  • amisulpride
  • cisapride
  • isocarboxazid
  • squill
  • tretinoin
  • tretinoin topical

Metolazone has moderate interactions with at least 153 different drugs.

Metolazone has mild interactions with at least 150 different drugs.

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns or for more information about this medicine.

What Are Warnings and Precautions for Metolazone?


  • This medication contains metolazone
  • Do not take Zaroxolyn if you are allergic to metolazone or any ingredients contained in this drug
  • Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately


  • Dcumented hypersensitivity to metolazone or sulfonamides
  • Failure of the kidneys to produce urine (anuria)
  • Hepatic coma or precoma.

Effects of Drug Abuse

  • No information available

Short-Term Effects

  • See "What Are Side Effects Associated with Using Metolazone?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Metolazone?"


  • Use with caution in diabetes mellitus, fluid or electrolyte imbalance, hypercholesterolemia, hyperuricemia or gout, low blood pressure (hypotension), systemic lupus erythematosus (SLE), previous sympathectomy, liver disease, renal disease
  • Avoid concurrent use with lithium (reduction of lithium dosage by 50% may be necessary)
  • May aggravate digitalis toxicity
  • Photosensitization may occur
  • Electrolyte disturbances (hyponatremia, hypochloremic alkalosis) may occur
  • Sensitivity reactions may occur with or without history of allergy or asthma
  • Patients allergic to sulfa may show cross-sensitivity
  • May deleteriously alter lipid/glucose metabolism
  • Mykrox not therapeutically interchangeable with Zaroxolyn
  • Risk of male sexual dysfunction

Pregnancy and Lactation

  • Metolazone use during pregnancy may be acceptable
  • Either animal studies show no risk but human studies were not available or animal studies showed minor risks and human studies were done and showed no risk
  • Metolazone use when breastfeeding is not recommended


The only purpose of the kidneys is to filter blood. See Answer
Medscape. Metolazone.
RxList. Metolazone Monograph.

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