Furosemide belongs to the class of medications called diuretics. It is used to treat edema (fluid retention) that occurs with congestive heart failure and disorders of the liver, kidney, and lung. It is also used to control mild to moderate high blood pressure. It may be used in combination with other medications to treat more severe high blood pressure.

Furosemide works by increasing the amount of urine produced and excreted, and by removing excessive water (edema) from the body. The tablet form begins to work within an hour of being taken and usually lasts for 4 to 6 hours. The injectable form begins to work within ½ hour and lasts approximately 2 hours.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The recommended adult starting dose for treating edema is 40 mg to 80 mg. If a satisfactory result occurs within 6 hours, the dose may be decreased or kept the same. If edema continues longer than 6 hours, the dose may be increased by 20 mg to 40 mg.

The recommended adult daily dose of furosemide ranges from 20 mg to 200 mg. Once the effective single dose has been determined, it may be taken 1 to 3 times a day.

When treating hypertension (high blood pressure), the dose of furosemide starts at 20 mg to 40 mg twice a day. Doses of 40 mg twice a day are generally considered the maximum dose to treat high blood pressure. If blood pressure hasn't been reduced enough with this dose, other medications may be added to further reduce blood pressure.

For children, the dose of furosemide used is based on body weight. The recommended dose is up to 2 mg per kilogram of body weight each day, divided into 2 to 4 equal doses.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones above, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not take furosemide if you:

• are allergic to furosemide or any ingredients of the medication
• are allergic to sulfonamide medications
• are an infant suffering from certain diseases (e.g., Rh incompatibility, familial non-hemolytic jaundice)
• are breast-feeding
• are jaundiced (have yellowing of the skin and eye pigments), especially newborn infants
• are suffering from dehydration
• have complete kidney shutdown
• have extremely low blood levels of sodium or potassium
• have hepatic coma or precoma
• have low blood pressure

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• constipation
• diarrhea
• dizziness or lightheadedness when getting up from a lying or sitting position
• increased amount of urine
• increased frequency of urination
• increased sensitivity of skin to sunlight
• dry mouth
• nausea
• sweating
• thirst
• tiredness
• vomiting

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• abdominal pain
• blurred vision
• confusion
• difficulty concentrating
• fast, slow, or irregular heartbeat
• muscle spasms (particularly in small children)
• painful or difficult urination
• poor weight gain (when given to premature babies)
• ringing or buzzing in ears or any loss of hearing
• signs of dehydration (e.g., confusion, dry mouth, thirst, muscle cramps, nausea, vomiting)
• signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
• skin rash or hives and itching
• symptoms of high blood sugar (e.g., frequent urination, increased thirst, excessive eating, unexplained weight loss, poor wound healing, infections, fruity breath odour)
• unexpected muscle pain or weakness
• unusual infections (fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiff neck, weight loss, or listlessness)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of a blood clot in blood vessels, such as sudden vision change or dizziness, chest pain, pain and swelling in one leg muscle
• signs of decreased kidney function (e.g., trouble breathing, swelling, fast or irregular heartbeat, confusion, decreased urination, decreased appetite)
• signs of a serious allergic reaction (i.e., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• signs of a severe skin reaction (i.e., rash, blisters, or red splotches on skin, blisters in mouth, eyes, ears, nose, eye irritation, swelling of eyelids, and flu-like symptoms)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Dehydration: Furosemide is a potent diuretic (water pill) which, if given in excessive amounts, can lead to large amounts of urination resulting in dehydration. Symptoms of dehydration include dry mouth, thirst, decreased urination, reduced tearing, and reduced sweating. Make sure you are drinking an adequate amount of water to prevent these symptoms. You may wish to discuss with your doctor what an appropriate fluid intake is for you.

Dementia: Studies have shown that when furosemide is taken with risperidone by people who are over 61 years of age there is an increased rate of death. The combination of these two medications should be avoided.

Diabetes: Furosemide may reduce blood sugar control for people with diabetes. If you have diabetes or are at risk for developing diabetes, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. You may be advised to increase the number of blood glucose checks that you do each day.

Drowsiness/reduced alertness: When you first start taking furosemide, it may cause drowsiness or dizziness, affecting your ability to drive or operate machinery. Avoid these and other hazardous tasks until you have determined how this medication affects you.

Fluid and electrolyte balance: This medication can affect the levels of electrolytes such as potassium, sodium, magnesium, chloride, and calcium. Your doctor will periodically check to see if these are in balance. Warning signs or symptoms of fluid and electrolyte imbalance include:

• confusion
• drowsiness
• dryness of mouth
• lethargy
• low blood pressure
• muscle pains or cramps
• muscular fatigue
• nausea and vomiting
• racing heartbeat
• restlessness
• seizures
• thirst
• weakness

During long-term treatment with furosemide, a high-potassium diet is recommended. You may also require potassium supplements. Your doctor will monitor your potassium levels through occasional blood tests.

Gout: An acute gout attack may occur in some patients taking furosemide. Symptoms of an acute gout attack include sudden pain, swelling, and stiffness in the affected joint, often the big toe. You may also experience a fever. If this is your first attack, seek medical attention as soon as possible. If you have had gout attacks before, follow your doctor's instructions for dealing with the attack.

Hearing Loss: Furosemide can cause temporary and permanent hearing loss over time. Permanent hearing loss may be more likely to occur with high, long-term doses of furosemide and when this medication is taken with other medications that can damage hearing. If you experience a change in your hearing, or a sensation of ringing in the ears, talk to your doctor as soon as possible.

Kidney function: This medication works directly on the kidneys and may cause decreased kidney function over time. Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. If you have reduced kidney function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: Decreased liver function can cause this medication to build up in the body, increasing the chance of side effects. If you have liver disease or reduced liver function, discuss with your doctor how this medication may affect your medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Sulfa medications: Furosemide is a sulfonamide derivative. Some people who are allergic to sulfonamides (such as sulpha antibiotics) also experience allergic reactions to furosemide. Before you take furosemide, inform your doctor about any previous adverse reactions you have had to medications, especially to other water pills or sulpha antibiotics. Contact your doctor at once if you experience signs of an allergic reaction, such as skin rash, itching, difficulty breathing, or swelling of the face and throat.

Pregnancy: The effect of taking furosemide on the unborn baby during pregnancy is unknown. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: Furosemide passes into breast milk and may also partially reduce the amount of breast milk produced. If you are a breast-feeding mother and are taking furosemide, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Seniors: Seniors may be more likely to experience increased side effects from furosemide.

There may be an interaction between furosemide and any of the following:

• acetylsalicylic acid (ASA)
• aldesleukin
• aliskiren
• allopurinol
• alpha blockers (e.g., alfuzosin, doxazosin, tamsulosin)
• alpha agonists (e.g., clonidine, methyldopa)
• aminoglycoside antibiotics (e.g., amikacin, gentamicin, tobramycin)
• amiodarone
• amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
• angiotensin converting enzyme (ACE) inhibitors (e.g., lisinopril, enalapril, fosinopril)
• angiotensin II receptor antagonists (e.g., irbesartan, losartan)
• antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• antiseizure medication (e.g., carbamazepine, phenobarbital, phenytoin, topirimate)
• apomorphine
• barbiturates (e.g., butalbital, phenobarbital)
• beta-adrenergic blockers (e.g., atenolol, propranolol, sotalol, timolol)
• beta2-agonists (e.g., formoterol, salbutamol, salmeterol)
• bismuth subsalicylate
• bortezomib
• brimonidine
• bromocriptine
• buprenorphine
• butorphanol
• calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
• cefuroxime
• chloral hydrate
• cholestyramine
• cisplatin
• colesevelam
• colestipol
• conivaptan
• corticosteroids (e.g., hydrocortisone, prednisone, fluticasone, budesonide)
• cyclosporine
• desmopressin
• diabetes medications (e.g., acarbose, canagliflozin, glyburide, linagliptin, lixisenatide, insulin, metformin)
• digoxin
• duloxetine
• foscarnet
• guanfacine
• iron sucrose
• ivabradine
• leflunomide
• levodopa
• lithium
• methadone
• methotrexate
• methylphenidate
• minoxidil
• monoamine oxidase inhibitors (MAOIs; e.g., phenelzine, rasagiline, selegiline, tranylcypromine)
• nabilone
• narcotic pain relievers (e.g., codeine, fentanyl, morphine, oxycodone, tapentadol, tramadol)
• nitrates (e.g., nitroglycerin, isosorbide dinitrate, isosorbide mononitrate)
• nonsteroidal anti-inflammatory medications (NSAIDs; e.g., celecoxib, ibuprofen, indomethacin, naproxen)
• obinutuzumab
• other diuretics (water pills; e.g., ethacrynic acid, hydrochlorothiazide, triamterene)
• paclitaxel
• paromomycin
• pentoxifylline
• phosphodiesterase-5 inhibitors (e.g., sildenafil, tadalafil, vardenafil)
• pramipexole
• ropinirole
• rotigotine
• sacubitril
• sodium phosphates
• sucralfate
• teriflunomide
• theophylline
• thyroid replacements (e.g., dessicated thyroid, levothyroxine)
• tizanidine
• tretinoin
• tricyclic antidepressants (e.g., clomipramine, imipramine)
• yohimbine

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than the ones listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.