Furoscix, Lasix

Introduction

Written by Sarah Lewis, PharmD
Medically reviewed by Victor Nguyen, PharmD, MBA
Updated on July 28, 2023

Furosemide (fyoor OH se mide) is a generic medication prescribed for high blood pressure and edema (fluid buildup) in adults and children. Furosemide belongs to a group of drugs called diuretics (water pills).

These approved uses differ based on the form of furosemide your doctor prescribes.

Boxed warning: Risk of fluid loss

Furosemide has a boxed warning about the risk of excessive fluid and electrolyte (salt and mineral) loss. Boxed warnings are the most serious warnings from the Food and Drug Administration (FDA).

For details, see the “Interactions and warnings for furosemide” section.

Side effects of furosemide

Furosemide may cause mild or serious side effects. More common mild side effects of furosemide 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 furosemide’s side effects, ask your doctor or pharmacist. You can also refer to the prescribing information for furosemide listed in the “Resources” section.

Mild side effects

More common mild side effects reported with some forms of furosemide are listed below.

This article doesn’t include all possible mild side effects of the drug. To learn more about furosemide’s side effects, refer to the prescribing information for furosemide 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.

Mild side effects of furosemide oral tablet and furosemide injection* include:

• constipation
• dizziness
• headache
• urinating more than usual
• mild allergic reaction†

* Furosemide injection is given into your muscle or vein.
† For details about this side effect, see the “Interactions and warnings for furosemide” section.

Serious side effects

Serious side effects of furosemide are listed below.

This article doesn’t include all possible serious side effects of the drug. To learn more about furosemide’s side effects, refer to the prescribing information for furosemide 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, furosemide’s serious side effects include:

• changes in blood cell counts
• high blood sugar
• high uric acid levels, which can cause gout
• kidney problems
• liver problems
• inflammation of the pancreas
• paresthesias (burning, prickling, or other unusual sensations)
• ringing in the ears or hearing loss
• sensitivity to sunlight, which can cause sunburn
• orthostatic hypotension (sudden low blood pressure upon standing)
• inflammation of blood vessels
• boxed warning: risk of excessive fluid and electrolyte (salt and mineral) loss*
• severe allergic reaction*

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

Common questions about furosemide

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

What is furosemide’s mechanism of action? How does the drug work?

Furosemide works in the kidneys to help the body get rid of extra fluid (water, salts, minerals, and more). The area where it works in the kidneys is called the loop of Henle. So you may hear furosemide called a loop diuretic.

Furosemide will start working within an hour of taking it.

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

Are there brand names available for furosemide?

Yes, furosemide oral tablet is available as the brand-name drug Lasix. To learn more about this brand-name medication, talk with your doctor or pharmacist.

Is furosemide safe for older adults?

Yes, furosemide is usually safe for older adults (age 65 years and older). But side effects, such as orthostatic hypotension (sudden low blood pressure upon standing), can be more common in older adults. Due to this risk, doctors usually start furosemide treatment at lower doses for older adults. They may also check kidney function more often in older adults.

If you have concerns about taking furosemide, talk with your doctor or pharmacist.

Uses of furosemide

The Food and Drug Administration (FDA) approves prescription drugs such as furosemide for certain conditions. Approved uses for furosemide are described below. These uses differ based on the form of furosemide prescribed.

Note: Doctors may not prescribe furosemide oral tablet, oral liquid, or injection in certain situations. This includes conditions in which the kidneys aren’t making urine. (Furosemide injection is given into your muscle or vein.)

Use for edema

Doctors may prescribe furosemide oral tablet, oral liquid, and injection for treating edema. It’s used for this purpose in adults and children. Doctors usually prescribe it as a long-term treatment.

Furosemide injection is usually a short-term treatment for people who can’t take medications by mouth.

With edema, too much fluid (water, salts, minerals, and more) builds up in the body’s tissues. This causes swelling, which most commonly affects the legs, ankles, and feet. Edema often happens with heart failure, liver disease, and kidney disease. Furosemide can help get rid of the extra fluid and relieve edema.

Use for high blood pressure

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

With high blood pressure, people usually don’t have symptoms. But having high blood pressure increases your risk of serious complications. These include heart attack and stroke. Lowering blood pressure with medications such as furosemide helps prevent complications.

Doctors can prescribe furosemide together with other high blood pressure medications.

Interactions and warnings for furosemide

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

Interactions of furosemide

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 furosemide, 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 furosemide” section below.

Warnings for furosemide

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

Boxed warning: Risk of fluid loss

Furosemide has a boxed warning about the risk of excessive fluid and electrolyte (salt and mineral) loss. Boxed warnings are the most serious warnings from the Food and Drug Administration (FDA).

Treatment with a diuretic such as furosemide helps get rid of extra fluid in your body. (Body fluid is a mixture of water, electrolytes, and more.) But the body can lose too much fluid. Overtreating with a diuretic increases the risk of this happening. Excessive fluid loss can cause dehydration and low blood volume (not enough blood circulating in your body). Either of these conditions is life threatening.

Due to this risk, it’s important to take furosemide exactly as your doctor prescribes. Your doctor will determine the right dosage for you.

Symptoms of dehydration or low blood volume may include:

• being thirstier than usual
• confusion
• dry mouth
• fast, pounding, or skipping heartbeats
• making less urine than usual
• muscle pain or cramping
• nausea or vomiting
• sleepiness
• weakness

If you experience the symptoms above, seek immediate medical care or call 911 or a local emergency number.

To learn more about the risk of fluid loss, talk with your doctor or pharmacist.

Other warnings

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

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

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

Allergic reaction

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

If you’ve had an allergic reaction to furosemide or any of its ingredients, your doctor will likely not prescribe furosemide. 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 furosemide, call your doctor right away. If you have severe symptoms, call 911 or a local emergency number.

Overdose of furosemide

If you take furosemide by mouth, you should not take more furosemide than your doctor prescribes. For some drugs, doing so may lead to harmful effects or overdose. To learn about furosemide’s side effects, see the “Side effects of furosemide” section.

If you think you’ve taken too much furosemide, 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 furosemide

Information about furosemide and pregnancy and breastfeeding is described below.

Furosemide and pregnancy

It’s not known whether furosemide is safe to take during pregnancy. If you’re planning a pregnancy or can become pregnant, talk with your doctor before taking this medication.

Furosemide and breastfeeding

You should not take furosemide 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 furosemide.

What to ask your doctor

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

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

• Is there anything I need to avoid while taking furosemide?
• Do I have an increased risk of furosemide side effects?
• How does furosemide compare to other medications that could treat my condition?

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
• Furosemide injection, USP. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/9fbc6985-64fd-4233-b401-8097a3895b8c/spl-doc
• Furosemide oral solution, USP. (2022). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/3fd02fb5-98a0-4eda-a0ec-41faabe04706/spl-doc
• Furosemide tablets, USP. 20mg, 40 mg, and 80 mg. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/febeaf8c-0f4b-cc40-e053-6394a90a873e/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.