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Generic name: metolazone [ me-TOL-a-zone ]
Brand names: Zaroxolyn, Mykrox
Dosage form: oral tablet (10 mg; 2.5 mg; 5 mg)
Drug class: Thiazide diuretics

Medically reviewed by on Aug 9, 2023. Written by Cerner Multum.

What is metolazone?

Metolazone is a thiazide diuretic (water pill) that helps prevent your body from absorbing too much salt, which can cause fluid retention.

Metolazone is used to treat fluid retention (edema) in people with congestive heart failure, or a kidney disorder such as nephrotic syndrome. Metolazone is also used to treat high blood pressure (hypertension).

Metolazone may also be used for purposes not listed in this medication guide.

Metolazone side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Metolazone may cause serious side effects. Call your doctor at once if you have:

Common side effects of metolazone may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


You should not use metolazone if you are unable to urinate, or if you have severe liver disease.

What should I discuss with my doctor before taking metolazone?

You should not use metolazone if you are allergic to it, or if you have:

To make sure metolazone is safe for you, tell your doctor if you have:

Using metolazone during pregnancy could cause side effects in the newborn baby, such as blood cell problems, or jaundice (yellowing of the skin or eyes). Tell your doctor if you are pregnant or if you become pregnant while using metolazone.

Metolazone can pass into breast milk and may harm a nursing baby. You should not breast-feed while using this medicine.

Metolazone is not approved for use by anyone younger than 18 years old.

How should I take metolazone?

Follow all directions on your prescription label. Your doctor may occasionally change your dose to make sure you get the best results. Do not use this medicine in larger or smaller amounts or for longer than recommended.

Metolazone is usually taken only once per day.

You may need to limit salt in your diet while taking this medicine. Follow your doctor's instructions carefully.

While using metolazone, you may need frequent blood tests. Your blood and urine may both be tested if you have been vomiting or are dehydrated.

Metolazone can cause unusual results with certain medical tests. Tell any doctor who treats you that you are using metolazone.

If you need surgery, tell the surgeon ahead of time that you are using metolazone. You may need to stop using the medicine for a short time.

If you are being treated for high blood pressure, keep using this medicine even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medicine for the rest of your life.

Store the tablets at room temperature away from heat, light, and moisture.

Metolazone dosing information

Usual Adult Dose for Hypertension:

Initial dose: 2.5 mg orally once a day (Zaroxolyn) or
0.5 mg orally once a day (Mykrox).

Usual Adult Dose for Edema:

Initial dose: 5 mg orally once a day (Zaroxolyn) or
0.5 mg orally once a day (Mykrox).

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include severe dizziness or drowsiness, dry mouth, thirst, muscle weakness, feeling light-headed, or fainting.

What should I avoid while taking metolazone?

Drinking alcohol with metolazone can cause side effects.

Avoid becoming overheated or dehydrated during exercise, in hot weather, or by not drinking enough fluids. Follow your doctor's instructions about the type and amount of liquids you should drink. In some cases, drinking too much liquid can be as unsafe as not drinking enough.

What other drugs will affect metolazone?

Taking this medicine with other drugs that make you make you light-headed can worsen this effect. Ask your doctor before taking metolazone with a narcotic pain medicine, muscle relaxer, or medicine for anxiety or seizures.

Tell your doctor about all your current medicines and any you start or stop using, especially:

This list is not complete. Other drugs may interact with metolazone, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.