Metolazone

Introduction

Written by Sarah Lewis, PharmD
Medically reviewed by Alex Brewer, PharmD, MBA
Updated on September 13, 2023

Metolazone (me TOLE a zone) is a generic medication prescribed for high blood pressure and edema (swelling due to fluid buildup) from kidney disease or heart failure. Metolazone belongs to a group of drugs called diuretics. Diuretics are commonly called “water pills.”

Common questions about metolazone

Below you’ll find answers to a few commonly asked questions about metolazone.

What brand names are available for metolazone?

There isn’t a brand-name drug available for metolazone. Metolazone is a generic version of the brand-name drug, Zaroxolyn. But this brand-name drug is no longer on the market.

A generic medication is an identical co­py of the active drug in a brand-name medication. (An active drug is the ingredient that makes a medication work.) Generic drugs are believed to be as effective and safe as brand-name drugs. And generic drugs typically cost less compared to brand-name drugs.

If you’d like to find out more about this, talk with your doctor or pharmacist.

How does metolazone work? And how long does it take to start working?

Metolazone’s mechanism of action (the way it works) is by making the kidneys remove more salt and fluid from your body. Getting rid of extra fluid relieves edema (swelling due to fluid buildup) and lowers blood pressure.

Metolazone should start working to increase fluid loss within an hour or so. The increase in fluid loss will cause you to start urinating more. This is a sign that metolazone is working. If you take metolazone for high blood pressure, it can take a few weeks to see its maximum effect on lowering blood pressure.

If you’d like to know more about how metolazone works, talk with your doctor or pharmacist.

Is metolazone similar to Lasix?

Yes, metolazone is similar to (furosemide) Lasix. They’re both diuretic drugs (“water pills”) that have similar uses. But they work in different ways. Because they work differently, doctors sometimes prescribe them together to increase fluid loss even more.

To learn more about how these two drugs compare, talk with your doctor or pharmacist.

Side effects of metolazone

Metolazone may cause mild or serious side effects. More common mild side effects of metolazone and its serious side effects are listed below. This article doesn’t include all possible side effects of the drug. Side effects can vary based on your age, overall health, and any other medications you take.

To learn more about metolazone’s side effects, ask your doctor or pharmacist. You can also refer to the prescribing information for metolazone listed in the “Resources” section.

Mild side effects

More common mild side effects reported with metolazone oral tablet are listed below.

This article doesn’t include all possible mild side effects of the drug. To learn more about metolazone’s side effects, refer to the prescribing information for metolazone listed in the “Resources” section.

With many drugs, mild side effects may go away within a few days or a couple of weeks. If the side effects bother you, tell your doctor or pharmacist. They may be able to suggest ways to manage them.

Metolazone oral tablet’s mild side effects include:

• constipation
• dizziness
• dry mouth
• headache
• mild allergic reaction*

* For details about this side effect, see the “Interactions and warnings for metolazone” section.

Serious side effects

Serious side effects of metolazone are listed below.

This article doesn’t include all possible serious side effects of the drug. To learn more about metolazone’s side effects, refer to the prescribing information for metolazone listed in the “Resources” section.

With many drugs, serious side effects are possible but not common. If you have serious side effects from this drug, call your doctor right away. If you’re having severe symptoms or a medical emergency, call 911 or a local emergency number.

In general, metolazone’s serious side effects include:

• dehydration
• high blood sugar levels
• high calcium levels
• high uric acid levels, which can increase the risk of gout attacks
• kidney problems
• liver problems
• low blood cell counts, including red blood cells, white blood cells, and platelets
• low magnesium levels
• low sodium or low potassium levels, which can be severe and happen very quickly
• nerve problems
• new or worsening systemic lupus erythematosus (an autoimmune disease)
• sudden low blood pressure when you stand up, which can lead to fainting
• severe allergic reaction*

* For details about this side effect, see the “Interactions and warnings for metolazone” section.

Uses of metolazone

The Food and Drug Administration (FDA) approves prescription drugs such as metolazone for certain conditions. Approved uses for metolazone are described below.

Use for edema

Doctors may prescribe metolazone oral tablet for treating edema (swelling due to fluid buildup). It’s used for this purpose in adults. It’s usually prescribed as a long-term treatment.

With edema, your body holds on to fluid. The extra fluid builds up in your tissues and causes swelling. The swelling can occur anywhere, but it often affects the feet, ankles, and lower legs. Metolazone can help relieve edema caused by kidney disease or heart failure.

Use for high blood pressure

Doctors may prescribe metolazone oral tablet for treating high blood pressure. It’s used for this purpose in adults. It’s usually prescribed as a long-term treatment.

With high blood pressure, people usually don’t have any symptoms. This means you can have it and not know it unless you check your blood pressure regularly. Having high blood pressure increases the risk of potentially fatal problems, such as heart attack or stroke. Lowering blood pressure with medications, including metolazone, can help prevent these problems.

Metolazone can be prescribed alone or together with other medications that treat high blood pressure.

Interactions and warnings for metolazone

Below, you’ll find information about metolazone’s possible interactions and warnings.

Interactions of metolazone

Certain things may affect how a drug works. These include getting vaccines, consuming alcohol or certain foods, or taking the drug with other medications. This effect is called a drug interaction.

Before you take metolazone, ask your doctor to check for possible interactions. Be sure to tell them about any of the following you take or use:

• prescription or over-the-counter drugs
• vitamins, herbs, or supplements

To learn about drug-condition interactions, see the “Warnings for metolazone” section below.

Warnings for metolazone

Some people should not take metolazone, and others should take it cautiously.

Metolazone could cause harm to people with certain health conditions. This effect is called a drug-condition interaction. Other factors can also affect whether metolazone is a safe option for you.

Ask your doctor about specific warnings for metolazone, and be sure to tell your doctor about your:

• current health, including any allergies to medications
• past health conditions or surgeries

Allergic reaction

Metolazone can cause an allergic reaction in some people. Severe allergic reactions are rare but possible.

If you’ve had an allergic reaction to metolazone or any of its ingredients, your doctor will likely not prescribe metolazone. They can tell you about medications that are safer options for you.

A mild allergic reaction may cause the following symptoms:

• skin rash
• itchiness
• flushing (temporary warmth, redness, or deepening of skin color)

A severe allergic reaction may cause the following symptoms:

• severe skin rashes that may blister and peel
• swelling under your skin, usually in your hands, feet, eyelids, or lips
• swelling of your mouth, throat, or tongue, which can cause breathing problems

If you have an allergic reaction to metolazone, call your doctor right away. If you have severe symptoms, call 911 or a local emergency number.

Overdose of metolazone

You should not take more metolazone than your doctor prescribes. For some drugs, doing so may lead to harmful effects or overdose.

If you think you’ve taken too much metolazone, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have concerning symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.

Pregnancy or breastfeeding and metolazone

Information about metolazone and pregnancy and breastfeeding is described below.

Metolazone and pregnancy

It’s not known whether metolazone should be taken during pregnancy. If you’re planning a pregnancy or can become pregnant, talk with your doctor before taking this medication.

Metolazone and breastfeeding

Metolazone should not be taken while breastfeeding. If you’re currently breastfeeding or planning to do so, talk with your doctor before taking this medication. Your doctor may recommend other ways to feed your child during treatment with metolazone.

What to ask your doctor

Let your doctor know if you have questions about metolazone or would like more details about it.

Here’s a list of some possible questions you may want to ask your doctor:

• How does metolazone compare with other diuretic drugs?
• What is the most important information I should know about metolazone?
• Do any of my other medications interact with metolazone?

Resources

• Food and Drug Administration. (2023). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/index.cfm
• Metolazone tablets, USP. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/51300edb-2b0f-427c-aeed-bc74a12f52ce/spl-doc

Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.