Furosemide

(fyur-oh-suh-mide)

Trade/other name(s): Lasix

Why would this drug be used?

Furosemide is a diuretic (water pill). Its main use is to help remove excess fluid from the body to treat swelling (edema) or high blood pressure. It can also be used to lower calcium blood levels when they are too high.

How does this drug work?

Furosemide causes the kidneys to keep more of certain electrolytes (sodium, potassium, chloride, calcium, and magnesium) out of the blood, leaving them in the urine. Water is drawn out along with these minerals. This leads to an increase in urine production and more fluid and electrolytes leaving the body.

Before taking this medicine

Tell your doctor…

• If you are allergic to any medicines, dyes, additives, or foods. People who are allergic to sulfonamide drugs (sulfadiazine, sulfamethoxazole, etc.) may also be allergic to furosemide.
• If you have ever had serious kidney disease or liver disease, such as cirrhosis. You may be more likely to have side effects from this drug.
• If you have ever had diabetes, gout, or systemic lupus erythematosus (SLE). These conditions may become worse while taking this drug.
• If you have any other medical conditions such as heart disease, congestive heart failure, lung disease, or infections. You may need closer monitoring of these conditions while being treated.
• If you plan to have surgery. Furosemide may interact with certain drugs used in surgery.
• If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. It is not known if this drug might cause problems if a woman takes it at the time of conception or during pregnancy. If you are sexually active while taking this drug, you should use some kind of birth control during treatment. It is important to check with your doctor about what kinds of birth control can be used with this medicine. This drug should be used during pregnancy only if the potential benefit is thought to justify the potential risk to the fetus.
• If you are breast-feeding. This drug passes into breast milk and may affect the baby. Talk with your doctor about the possible risks of breast-feeding while taking this drug.
• About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs. In fact, keeping a written list of each of these medicines (including the doses of each and when you take them) with you in case of emergency may help prevent complications if you get sick.

Interactions with other drugs

Furosemide may interact with a number of other drugs, so be sure your doctor is aware of all of the medicines and supplements you are taking.

This drug may raise the risk of hearing loss if taken with ethacrynic acid (Edecrin, another diuretic), amphotericin B (an IV anti-fungal drug), or aminoglycoside antibiotics such as streptomycin, tobramycin, amikacin, neomycin, and gentamicin.

This drug could cause blood pressure to drop too low if used along with certain blood pressure or heart medicines.

This drug may affect the kidneys if used along with high doses of non-steroidal anti-inflammatory drugs (NSAIDS) such as aspirin or ibuprofen.

Furosemide should be used with caution in patients taking lithium, as it may raise blood lithium levels.

This drug can lower blood levels of potassium, and must be used carefully if other drugs affecting potassium levels are also being taken.

Use of the ulcer drug sucralfate may make furosemide less effective. If you are taking sucralfate, take your doses of furosemide and sucralfate at least 2 hours apart.

Furosemide may change the effects of some drugs used for anesthesia. Be sure your doctors know you are taking this drug before you have surgery.

There may be other drug interactions as well. Check with your doctor, nurse, or pharmacist about all of your medicines, herbs, and supplements, and whether alcohol can cause problems with this medicine.

Interactions with foods

No serious interactions with foods are known at this time. Check with your doctor, nurse, or pharmacist about whether some foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Furosemide can be taken by mouth as a pill or liquid, or it can be given in a vein (intravenous, or IV) or muscle (intramuscular, or IM). The starting dose and the way the drug is given depends on a number of factors, such as age, body size, kidney and liver function, why the drug is being used, and how quickly the effect is needed. The dose may need to be adjusted based on the body’s response to the drug.

If you are taking furosemide to help remove calcium from the blood, you will likely get an IV infusion of salt water (normal saline) at the same time, which will help take calcium out of the body.

Your doctor may advise you to eat a diet high in potassium or take potassium supplements, or you may be given potassium or other electrolytes in your IV fluid. This is to replace what is lost in the urine.

Store the medicine tightly closed, away from heat and moisture and away from children and pets.

Precautions

Furosemide causes certain electrolytes (potassium, calcium, etc.) to be lost along with the urine, which can lead to low levels of these substances in the body. Symptoms might include dry mouth, thirst, feeling tired or weak, restlessness, muscle pains or cramps, rapid heart rate, little or no urine output, nausea, or vomiting. Let your doctor or nurse know right away if you notice any of these symptoms.

Your doctor will also test your blood throughout your treatment, looking for possible effects of the drug on blood electrolyte levels. Based on the test results, your doctor may need to change your dose of this drug.

Because it causes the body to get rid of fluid, this drug may cause dehydration and a drop in blood pressure. This may cause you to fell dizzy, lightheaded, or even faint if you sit up or stand up too quickly. Alcohol and other drugs that make you sleepy or slow the nervous system may make this effect worse. Changing position slowly can reduce the risk of these problems.

This drug may make you very sensitive to sunlight. Do not spend long periods in the sun until you know how your skin is reacting to sunlight. Your doctor may advise you to avoid being outdoors between the hours of 10 and 4, use sunscreen, and/or to wear sunglasses, a hat, and protective clothes when outside, even on hazy days.

Call your doctor if you notice a rash or blisters. This may happen along with a sore throat or fever.

People with diabetes should be aware that furosemide may raise blood glucose levels.

People who have gout should be cautious when taking this medicine. This drug may raise your uric acid level and your risk of having an attack.

In some cases this drug may affect your hearing, especially if taken in high doses or if used along with other drugs that can affect hearing. Tell your doctor right away if you notice any change in your hearing, including ringing in your ears.

Possible side effects

You will probably not have most of the following side effects, but if you have any talk to your doctor or nurse. They can help you understand the side effects and cope with them.

Common

• passing urine more often
• feeling dizzy or lightheaded when sitting up or standing (due to blood pressure changes)*

Less common

• loss of electrolytes (potassium, sodium, chloride, magnesium, calcium) from the blood, which shows up on lab tests (Your doctor will explain the importance of these findings, if any.)*
• headache
• loss of appetite
• stomach cramps
• diarrhea
• increased uric acid in the blood (may raise the risk of gout attacks)*
• increased blood glucose levels*

Rare

• ringing in the ears (tinnitus) or hearing loss, especially if high doses are used*
• vision changes (blurred vision, yellowing of vision)
• blood test results showing the drug may be affecting your pancreas (Your doctor will explain the importance of these findings, if any.)*
• muscle spasms
• itching
• increased sensitivity to sunlight with higher risk of sunburn*
• serious rash with peeling skin*
• allergic reaction (hives, skin rash, or itching)

*See "Precautions" section for more detailed information.

There are some other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved before 1984 (FDA cannot verify dates of drugs approved before 1984).

Disclaimer: This information does not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.