Zaroxolyn (Metolazone) - Oral

What Is Zaroxolyn?

Zaroxolyn (metolazone) is a tablet available by prescription to treat high blood pressure and reduce extra fluid associated with heart failure and kidney diseases.

Zaroxolyn is a diuretic (also sometimes referred to as a “water pill”). It gets rid of excess fluid by preventing sodium from being absorbed in the kidneys, allowing excess water and electrolytes to be excreted in the urine. The removal of excess fluid in the veins causes a decrease in blood volume returning to the heart. As a result, the heart does not release as much blood to the arteries as it used to, which helps lower blood pressure.

Typically, a medication called a loop diuretic is used first to treat signs of excess fluid retention caused by heart failure. If the loop diuretic fails to relieve the excess fluid, metolazone can be given along with the medication. If you are taking both diuretics at the same time, your healthcare provider may carefully monitor for too much fluid loss.

Drug Facts

Generic Name: Metolazone

Brand Name(s): Zaroxolyn

Administration Route: Oral

Drug Availability: Prescription

Therapeutic Classification: Diuretic

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Metolazone

Dosage Form: Tablet

What Is Zaroxolyn Used For?

The Food and Drug Administration (FDA) approved Zaroxolyn to treat:

  • Edema (excess fluid) associated with congestive heart failure
  • Edema (excess fluid) associated with kidney disease, including nephrotic syndrome and states of diminished kidney function
  • High blood pressure
Zaroxolyn (Metolazone) Drug Information - Illustration by Zoe Hansen

Verywell / Zoe Hansen

How to Take Zaroxolyn

Since each dose is specialized to your indication and response to the medication, you should follow your healthcare provider's directions on how to take Zaroxolyn.

Generally, a single daily dose by mouth of Zaroxolyn is recommended. Whether you are taking it for edema related to heart failure or kidney disease, the maximum daily dose should be 20 milligrams (mg). If you take it for high blood pressure, the maximum daily dose should be 5 milligrams.

You can take Zaroxolyn with water and with or without food. However, you should not take this medication with alcohol because it can increase the risk of orthostatic hypotension, a feeling of dizziness or lightheadedness when quickly getting up from a sitting or standing position. Since Zaroxolyn gets rid of excess fluid, you may experience frequent urination, so it is best to take this medication in the morning or afternoon to avoid frequent trips to the bathroom in the middle of the night.


Store Zaroxolyn at room temperature and away from light. You should avoid storing this medication in areas with moisture, such as a medicine cabinet in a bathroom. Keeping your medication in hot or cold areas can reduce how well the drug works. Make sure your medication is stored in a safe place where children and pets can not reach to avoid accidental consumption. 

Off-Label Uses

Zaroxolyn is approved to treat excess fluid retention associated with heart failure and kidney disease. However, it has been studied for use in other disease states. These are considered "off-label" uses because the FDA has not approved Zaroxolyn for these conditions.

Metolazone has been studied for its use in treating:

  • Edema (excess fluid) associated with liver disease
  • Certain types of kidney stones
  • Premenstrual syndrome, commonly known as PMS

How Long Does Zaroxolyn Take to Work?

Frequent urination may occur within one hour of taking Zaroxolyn (if taken for excess fluid retention) and can continue throughout the day. When taking Zaroxolyn for high blood pressure, the time until results can vary from three to four days to three to six weeks.

What Are the Side Effects of Zaroxolyn?

This is not a complete list of side effects and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the FDA at or 1-800-FDA-1088.

Common Side Effects

The following side effects are commonly reported while taking Zaroxolyn:

  • Constipation
  • Diarrhea
  • Drowsiness
  • Dizziness 
  • Fatigue
  • Headache

Severe Side Effects

Do not hesitate to contact your healthcare provider right away if you are experiencing any of these rare but serious side effects. Call 911 immediately if you feel your life is at risk or you believe you're in need of medical assistance.

Rare but serious side effects can include but are not limited to:

  • Irregular heartbeat
  • Fainting
  • Unable to pass urine
  • Blood in urine
  • Vomiting
  • Blistered or peeling skin
  • Numbness in the hands or feet
  • Chest pain or pressure

Long-Term Side Effects

Taking Zaroxolyn for an extended time may cause you to experience hyponatremia, which is a condition when your sodium levels in the blood are lower than normal. Low potassium levels (hypokalemia) can also occur.

Report Side Effects

Zaroxolyn may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Zaroxolyn Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (tablets):
    • For fluid retention (edema):
      • Adults—At first, 5 to 20 milligrams (mg) once a day. Your doctor may adjust your dose if needed.
      • Children—Use and dose must be determined by your doctor .
    • For high blood pressure:
      • Adults—At first, 2.5 to 5 milligrams (mg) once a day. Your doctor may adjust your dose if needed.
      • Children—Use and dose must be determined by your doctor .


You should not take Zaroxolyn if you are pregnant or breastfeeding. This medication can cross through the placenta and breast milk, leading to unwanted adverse effects on the fetus or infant.

In children, Zaroxolyn is usually given at a lower dose of 0.05 to 0.1 milligrams/kilograms (kg) once a day. The healthcare provider will determine the correct dosing for your child.

Zaroxolyn is heavily excreted through the kidneys. People with impaired kidney function should avoid taking Zaroxolyn for this reason.

Missed Dose

If you happen to miss a dose, you will be okay. Take it as soon as you remember. If it is close to the time of your next dose, skip the missed dose and continue your normal daily dosing. Do not double up on doses to make up for missed doses. It is important only to take one tablet by mouth once a day. Do not take two or more tablets at the same time.

Overdose: What Happens If I Take Too Much Zaroxolyn?

There is no set overdose level that indicates you have taken too much Zaroxolyn. However, taking more than the recommended dose can lead to serious adverse effects such as:

  • Orthostatic hypotension
  • Dizziness
  • Fainting
  • Hypoventilation leading to coma
  • Stomach irritation

What Happens If I Overdose on Zaroxolyn?

If you think you or someone else may have overdosed on Zaroxolyn, call a healthcare provider or the Poison Control Center (1-800-222-1222).

If someone collapses or isn't breathing after taking Zaroxolyn, call 911 immediately.


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It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly. Blood or urine tests may be needed to check for unwanted effects .

Check with your doctor right away if you have any of the following symptoms while taking this medicine: convulsions or seizures; decreased urine; drowsiness; dry mouth; excessive thirst; muscle pains or cramps; nausea or vomiting; increased heart rate or pulse; or unusual tiredness or weakness. These may be symptoms of a condition called hypokalemia or potassium loss .

Dizziness, lightheadedness, or fainting may occur, especially when you get up from a lying or sitting position. Getting up slowly may help. If the problem continues or gets worse, check with your doctor .

Drinking alcoholic beverages may also make the dizziness, lightheadedness, or fainting worse. While you are taking this medicine, be careful to limit the amount of alcohol you drink .

This medicine may cause changes in your blood sugar levels. If you notice a change in the results of your blood or urine sugar tests or if you have any questions, check with your doctor .

Before you have any medical tests, tell the medical doctor in charge that you are taking this medicine. The results of some tests (e.g., tests for parathyroid function) may be affected by this medicine .

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements .

What Are Reasons I Shouldn’t Take Zaroxolyn?

Before taking any medication, it is important to talk to your healthcare provider about any other medical conditions you have. Certain conditions can cause unwanted side effects when taking Zaroxolyn or prevent the medication from working properly.

You should avoid taking Zaroxolyn if you have:

What Other Medications Interact With Zaroxolyn?

Zaroxolyn helps lower your blood pressure by reducing the blood volume returning to the heart. Therefore, taking other high blood pressure medications should be avoided because it can further lower your blood pressure.

Common high blood pressure medications include:

  • Prinivil, Qbrelis, Zestril (lisinopril)
  • Lotensin (benazepril)
  • Avapro (irbesartan)
  • Katerzia, Norliqva, Norvasc (amlodipine)

Since Zaroxolyn gets rid of excess water and electrolytes, medications sensitive to electrolyte loss can be potential drug interactions. Taking these medications listed below may prevent or enhance the efficacy of the drug or cause potential risks:

  • Anticoagulants, or blood thinners (e.g., warfarin)
  • Corticosteroids (e.g., prednisone)
  • Cardiac glycosides, or medications to treat certain irregular heartbeats and heart failure (e.g., digoxin)
  • Non-steroid anti-inflammatory drugs, or NSAIDs (e.g., ibuprofen)

This list is not not a complete list of all possible medications that interact with Zaroxolyn. It is important to let your healthcare provider or pharmacist know what medications, herbs, or supplements you are currently taking.

What Medications Are Similar?

People who are first diagnosed with fluid overload due to heart failure are typically administered a medication class called loop diuretics. Common loop diuretics include:

  • Furocot, Lasix (furosemide) 
  • Bumex (bumetanide)
  • Demadex, Soaanz (torsemide)

If the loop diuretic fails to eliminate the excess fluid, Zaroxolyn may be administered along with the medication. A person taking both Zaroxolyn and a loop diuretic should be monitored for excess fluid loss. However, loop diuretics should not be taken at the same time if you are already taking Zaroxolyn.

Chlorothiazide, an intravenous thiazide diuretic, can also be used with a loop diuretic if the medication is not working on its own. Chlorothiazide is also used to treat excess fluid retention and high blood pressure. While chlorothiazide can be an alternative to Zaroxolyn, Zaroxolyn oral tablets are significantly cheaper and should be used as a first-line option when loop diuretics fail.

Frequently Asked Questions

  • Is it safe to take ibuprofen while taking Zaroxolyn?

    Advil or Motrin, also known as ibuprofen, is safe to take with Zaroxolyn in low amounts. Ibuprofen and metolazone are broken down in the kidneys. Therefore, you should avoid high doses of ibuprofen because taking too much can damage your kidneys. Please consult with your healthcare provider for further information on your specific health condition.

  • Are there any special diet instructions while taking Zaroxolyn?

    It is recommended to consume a low-salt diet to reduce fluid overload in the body and high blood pressure. Furthermore, Zaroxolyn can lower your potassium levels which may cause heart arrhythmias. Therefore, you should also take potassium supplements or potassium-rich foods in your diet to prevent this unwanted effect.

  • How much does Zaroxolyn cost?

    The brand Zaroxolyn is an expensive medication, while the generic metolazone is generally cheaper. It is recommended to take generic medications over the brand as generic metolazone will be the most affordable option.

How Can I Stay Healthy While Taking Zaroxolyn?

To stay healthy while taking Zaroxolyn, it is important to take this medication as instructed by your healthcare provider. Continue taking your medication even if you feel well. Stopping too early can lengthen your medication therapy.

In addition, you can incorporate lifestyle changes to feel better faster, such as light exercise and a low-sodium diet. It might be difficult to change your lifestyle, but it does not hurt to start small and gradually work your way up to making healthier choices. Your healthcare provider can let you know what level of activity and lifestyle change would be right for you.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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