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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Loop Diuretic [EPC]
Furosemide is a potent loop diuretic (water pill) used to treat fluid retention (edema) associated with heart failure, liver disease, and kidney disorders. It is also utilized in the management of hypertension by promoting the excretion of water and salts.
Name
Furosemide
Raw Name
FUROSEMIDE
Category
Loop Diuretic [EPC]
Drug Count
4
Variant Count
203
Last Verified
February 17, 2026
RxCUI
1719286, 1719290, 1719291, 2683305, 2683306, 197732, 310429, 313988, 197730, 197731, 200801, 200809, 205732, 2725542, 2725546, 2621022, 2621028
UNII
7LXU5N7ZO5
About Furosemide
Furosemide is a potent loop diuretic (water pill) used to treat fluid retention (edema) associated with heart failure, liver disease, and kidney disorders. It is also utilized in the management of hypertension by promoting the excretion of water and salts.
Detailed information about Furosemide
References used for this content
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Furosemide.
Furosemide is a highly potent pharmaceutical agent classified as a loop diuretic (often referred to colloquially as a 'water pill'). It is primarily utilized in clinical settings to manage fluid overload, a condition known as edema, which is frequently associated with congestive heart failure, hepatic cirrhosis (advanced liver scarring), and various forms of renal (kidney) disease. Beyond its role in fluid management, Furosemide is also indicated for the treatment of hypertension (high blood pressure), either as a primary therapy or in conjunction with other antihypertensive medications.
Historically, Furosemide was developed in the early 1960s and received its initial approval from the U.S. Food and Drug Administration (FDA) in 1966. Since its introduction, it has become a cornerstone of cardiovascular and renal pharmacotherapy due to its rapid onset of action and significant efficacy in promoting diuresis (increased urine production). It belongs to the 'loop' class of diuretics because its primary site of action is located within the Loop of Henle, a specific U-shaped segment of the nephron in the kidney responsible for concentrating urine.
To understand how Furosemide works, one must understand the basic physiology of the kidney. The kidney filters blood to remove waste, but it also reabsorbs essential salts and water to maintain homeostasis (internal balance). Furosemide exerts its pharmacological effect by inhibiting the sodium-potassium-chloride (Na+/K+/2Cl-) cotransporter, specifically the NKCC2 isoform, located in the thick ascending limb of the Loop of Henle.
Under normal conditions, this transporter is responsible for reabsorbing approximately 25% of the sodium filtered by the kidneys. By blocking this transporter, Furosemide prevents the reabsorption of these electrolytes. Because water naturally follows salt (osmosis), the high concentration of sodium and chloride remaining in the renal tubule forces a significant volume of water to stay within the tubule as well. This leads to a profound increase in the excretion of water, sodium, chloride, magnesium, and calcium. The resulting reduction in extracellular fluid volume decreases the workload on the heart and reduces the pressure within the blood vessels, effectively treating both edema and hypertension.
Furosemide is absorbed from the gastrointestinal tract following oral administration, though its bioavailability (the fraction of the drug that reaches systemic circulation) can vary significantly between individuals, typically ranging from 40% to 70%. The presence of food can delay the absorption of Furosemide but generally does not significantly reduce the total amount absorbed. However, in patients with severe heart failure, gut edema (swelling of the intestinal walls) can further impair and delay absorption, sometimes requiring a transition to intravenous administration.
Once in the bloodstream, Furosemide is highly protein-bound, primarily to albumin (more than 91% to 99%). This high degree of protein binding is clinically significant because the drug must be secreted into the renal tubule to reach its site of action; it cannot simply be filtered at the glomerulus. It does not cross the blood-brain barrier to any significant extent but does cross the placental barrier.
Furosemide undergoes minimal hepatic (liver) metabolism. A small portion is converted into a glucuronide metabolite in the kidneys. Unlike many other drugs, it does not rely heavily on the Cytochrome P450 (CYP) enzyme system, which reduces the risk of certain metabolic drug-drug interactions, though other types of interactions remain common.
The elimination half-life of Furosemide is relatively short, typically ranging from 0.5 to 2 hours in healthy individuals. However, this half-life can be significantly prolonged in patients with renal or hepatic impairment. Approximately 60% to 90% of an intravenous dose is excreted unchanged in the urine, with the remainder eliminated via the feces.
Furosemide is FDA-approved for several critical indications:
Off-label uses, which are not FDA-approved but may be utilized by healthcare providers based on clinical judgment, include the acute management of hypercalcemia (excessively high calcium levels in the blood) and the treatment of forced diuresis in certain poisoning scenarios.
Furosemide is available in multiple formulations to accommodate different clinical needs:
> Important: Only your healthcare provider can determine if Furosemide is right for your specific condition. Regular monitoring of electrolytes and kidney function is essential during therapy.
Dosage for Furosemide must be highly individualized based on the patient's clinical response and the severity of the condition being treated.
For the treatment of edema in adults, the typical starting oral dose is 20 mg to 80 mg administered as a single dose. If a satisfactory response is not achieved, the healthcare provider may increase the dose by increments of 20 mg to 40 mg every 6 to 8 hours until the desired diuretic effect is reached. Once the edema is controlled, the effective dose may be administered once or twice daily as a maintenance regimen. In some severe cases, daily doses may reach up to 600 mg, though such high doses require intensive medical supervision.
The usual initial dose for hypertension is 40 mg twice daily. The healthcare provider will then adjust the dosage based on the blood pressure response. If the patient does not respond adequately, other antihypertensive agents may be added to the regimen. It is important to note that the blood-pressure-lowering effects of Furosemide may take several days to become fully apparent.
Furosemide is approved for use in pediatric patients, including neonates. The standard initial dose for edema in children is 2 mg/kg of body weight, administered as a single dose. If the response is inadequate, the dose may be increased by 1 mg/kg or 2 mg/kg every 6 to 12 hours. The maximum pediatric dose is generally capped at 6 mg/kg of body weight. For neonates, the dosing interval may be extended due to slower clearance rates in newborns.
In patients with severe renal impairment, higher doses of Furosemide are often required to achieve a diuretic effect because the drug has difficulty reaching its site of action within the nephron. However, clinicians must exercise caution to avoid toxicity. In cases of acute renal failure, the dose is carefully titrated to maintain urine output.
Patients with hepatic cirrhosis must be monitored very closely. Sudden alterations in fluid and electrolyte balance can precipitate hepatic encephalopathy (brain dysfunction caused by liver failure) or hepatorenal syndrome. Dosing is usually started at the lower end of the spectrum and increased very gradually.
Geriatric patients are generally started on the lowest possible effective dose. The elderly are more susceptible to the dehydrating effects of Furosemide, which can lead to orthostatic hypotension (dizziness upon standing) and an increased risk of falls. Renal function should be assessed before and during treatment.
Furosemide should be taken exactly as prescribed by a healthcare provider.
If a dose of Furosemide is missed, it should be taken as soon as the patient remembers. However, if it is almost time for the next scheduled dose, the missed dose should be skipped. Patients should never 'double up' on doses to make up for a missed one, as this significantly increases the risk of dehydration and electrolyte imbalance.
An overdose of Furosemide can lead to profound diuresis, resulting in severe dehydration, volume depletion, and electrolyte disturbances (such as dangerously low potassium or sodium levels). Symptoms of overdose may include extreme dizziness, fainting, weakness, confusion, or a rapid/irregular heartbeat. In the event of a suspected overdose, emergency medical services should be contacted immediately. Treatment typically involves fluid and electrolyte replacement in a clinical setting.
> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or stop taking the medication without medical guidance, as this can lead to a rapid rebound of fluid retention.
Because Furosemide is a potent diuretic, its most common side effects are related to its primary action of removing water and salt from the body. Many patients will experience:
Some patients may experience secondary effects as the body adjusts to the medication:
These effects are infrequent but require medical awareness:
> Warning: Stop taking Furosemide and call your doctor immediately if you experience any of the following serious reactions:
Prolonged use of Furosemide requires careful monitoring to prevent chronic complications:
Furosemide carries a significant FDA Black Box Warning regarding its potency:
Warning: Furosemide is a potent diuretic which, if given in excessive amounts, can lead to a profound diuresis with water and electrolyte depletion. Therefore, careful medical supervision is required, and dose and dose schedule must be adjusted to the individual patient's needs. (Source: FDA Labeling).
This warning emphasizes that Furosemide is not a 'mild' medication and must be managed with precise clinical oversight to avoid life-threatening dehydration.
Report any unusual symptoms to your healthcare provider. Regular blood tests are necessary to ensure your electrolyte levels remain within a safe range.
Furosemide is a powerful medication that requires strict adherence to safety protocols. Patients must be aware that this drug does not just remove water; it removes vital minerals. Sudden changes in these minerals can affect heart rhythm and brain function. It is essential to stay hydrated as directed by a doctor—neither over-drinking nor under-drinking fluid—and to attend all scheduled follow-up appointments for blood work.
As noted in the side effects section, Furosemide contains a Black Box Warning from the FDA. This is the most serious type of warning issued by the FDA. It highlights that Furosemide can cause severe loss of body water and salt. This can lead to serious medical problems if the dose is not perfectly matched to the patient's specific needs. Patients should never share this medication with others, as a dose that is safe for one person could be fatal for another.
Furosemide is a sulfonamide derivative. While many patients with a 'sulfa allergy' (usually to sulfonamide antibiotics like Bactrim) can tolerate Furosemide, there is a theoretical risk of cross-reactivity. Patients should inform their doctor of any history of allergic reactions to sulfa drugs. Symptoms of an allergic reaction include skin rashes, itching, or shortness of breath.
Hearing impairment and tinnitus (ringing in the ears) have been reported. This risk is highest with rapid intravenous injection, very high doses, or in patients with severely impaired kidney function. It is also increased when Furosemide is used alongside other drugs that can damage hearing, such as aminoglycoside antibiotics.
Patients taking Furosemide must undergo regular laboratory monitoring, typically including:
Furosemide can cause dizziness, blurred vision, or lightheadedness, especially during the first few days of treatment or when the dose is increased. Patients should not drive or operate heavy machinery until they are certain how the medication affects them.
Alcohol should be avoided or strictly limited while taking Furosemide. Alcohol acts as a mild diuretic itself and can also lower blood pressure. Combining alcohol with Furosemide significantly increases the risk of severe dizziness, fainting, and dehydration.
Furosemide should not be stopped abruptly unless directed by a physician. Sudden discontinuation can lead to a 'rebound' effect, where fluid retention and swelling return rapidly and more severely. If the medication needs to be stopped, healthcare providers usually recommend a gradual tapering of the dose.
> Important: Discuss all your medical conditions, especially kidney disease, liver disease, diabetes, or gout, with your healthcare provider before starting Furosemide.
Certain medications should never be used with Furosemide due to the high risk of severe adverse events:
Furosemide can interfere with certain laboratory tests, potentially leading to inaccurate results:
For each major interaction, the management strategy usually involves more frequent blood monitoring or adjusting the timing of doses.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. Even over-the-counter pain relievers can significantly impact how Furosemide works in your body.
There are specific clinical scenarios where Furosemide must NEVER be used because the risks far outweigh any possible benefits:
These are conditions where the drug should be used only with extreme caution and intensive monitoring:
As a sulfonamide derivative, there is a potential for cross-sensitivity with other sulfa-containing drugs. While the risk of a person with a 'sulfa' skin rash reacting to Furosemide is relatively low (estimated at less than 10%), patients who have had life-threatening reactions to sulfonamides should be evaluated carefully by an allergist before starting Furosemide.
> Important: Your healthcare provider will evaluate your complete medical history, including kidney function and allergy history, before prescribing Furosemide to ensure it is safe for you.
Furosemide is classified as FDA Pregnancy Category C. This means that animal reproduction studies have shown an adverse effect on the fetus, and there are no adequate and well-controlled studies in humans.
Caution is advised for nursing mothers. Furosemide passes into breast milk. Furthermore, because it is a potent diuretic, it can suppress lactation (reduce the amount of milk the mother produces). If the use of Furosemide is essential, the healthcare provider may recommend monitoring the infant for dehydration or considering alternative feeding methods.
Furosemide is frequently used in children, including premature infants. However, there are unique risks:
Patients over the age of 65 are at the highest risk for adverse effects from Furosemide.
In patients with chronic kidney disease (CKD), Furosemide is often necessary but difficult to manage. As the Glomerular Filtration Rate (GFR) drops, the amount of Furosemide that reaches the 'inside' of the kidney tubule decreases. This often requires 'high-dose' therapy (e.g., 80 mg to 240 mg or more) to achieve the same effect that 20 mg would have in a healthy person. However, these high doses increase the risk of side effects like hearing loss.
In patients with liver disease, Furosemide is often paired with another diuretic called Spironolactone. This combination helps maintain potassium balance. Patients with cirrhosis must be monitored for signs of hepatic encephalopathy, as even minor electrolyte imbalances can trigger mental confusion or coma.
> Important: Special populations require individualized medical assessment and more frequent laboratory monitoring to ensure safety.
Furosemide is a potent 'loop' diuretic that acts on the thick ascending limb of the Loop of Henle in the kidney's nephron. At the molecular level, it binds to and inhibits the Na+/K+/2Cl- cotransporter (NKCC2). This transporter is responsible for moving sodium, potassium, and chloride ions from the urine back into the blood. By blocking this transport, Furosemide ensures these ions remain in the urine. Because of the osmotic gradient, water is 'pulled' into the urine to follow the salt. This results in a massive increase in the excretion of water and electrolytes. Furosemide also increases the excretion of magnesium and calcium and can increase renal blood flow by stimulating the production of vasodilatory prostaglandins.
| Parameter | Value |
|---|---|
| Bioavailability | 40% - 70% (Oral) |
| Protein Binding | 91% - 99% (Primarily Albumin) |
| Half-life | 0.5 - 2.0 hours (Prolonged in renal/heart failure) |
| Tmax (Time to peak) | 1.0 - 2.0 hours |
| Metabolism | Minimal (Glucuronidation in Kidney) |
| Excretion | Renal (60-90%), Fecal (7-15%) |
Furosemide is the prototypical member of the Loop Diuretic class. Other medications in this class include Bumetanide (Bumex) and Torsemide (Demadex). While all loop diuretics work on the same part of the kidney, Furosemide is the most widely used due to its long history of clinical data and availability in various forms.
Medications containing this ingredient
Common questions about Furosemide
Furosemide is primarily used to treat edema, which is the accumulation of excess fluid in the body's tissues. This condition is commonly caused by heart failure, liver cirrhosis, or kidney disease. By helping the kidneys remove extra water and salt through urine, Furosemide reduces swelling in the legs, arms, and abdomen, and helps clear fluid from the lungs to improve breathing. Additionally, it is prescribed to treat hypertension (high blood pressure), which helps prevent future strokes, heart attacks, and kidney problems. It is a potent medication that is usually reserved for cases where milder diuretics are insufficient.
The most frequent side effects of Furosemide include increased frequency of urination, dizziness, lightheadedness, and headache. Many patients also experience symptoms of electrolyte imbalance, such as muscle cramps, weakness, or tiredness, often due to low potassium levels. Because it removes fluid rapidly, some people may feel excessively thirsty or develop a dry mouth. It is also common to experience a temporary drop in blood pressure when standing up quickly, which can cause a brief feeling of faintness. Most of these effects can be managed by adjusting the dose or timing under a doctor's supervision.
It is generally advised to avoid or strictly limit alcohol consumption while taking Furosemide. Alcohol has its own diuretic properties, which can worsen the dehydration caused by the medication. More importantly, alcohol can cause blood vessels to dilate, leading to a significant drop in blood pressure when combined with Furosemide. This increases the risk of severe dizziness, fainting, and accidental falls. If you choose to drink, you must discuss it with your healthcare provider to understand your specific risks based on your medical history.
Furosemide is classified as a Category C medication, meaning it is generally not recommended during pregnancy unless the benefits clearly outweigh the risks. It can cross the placenta and may affect the baby's growth or blood circulation. It is typically not used to treat the standard swelling that occurs during a healthy pregnancy. If you are pregnant or planning to become pregnant, you must inform your doctor immediately. They will likely explore safer alternatives for managing fluid or blood pressure during your pregnancy.
Furosemide is known for its rapid onset of action. When taken as an oral tablet, you will typically notice an increase in the urge to urinate within 30 to 60 minutes, with the peak effect occurring around 1 to 2 hours after ingestion. If administered intravenously in a hospital setting, the effects begin much faster, usually within 5 minutes. The diuretic effect of a single oral dose generally lasts for about 6 to 8 hours. Because of this relatively short duration, some patients may be required to take the medication twice a day.
You should never stop taking Furosemide suddenly without consulting your healthcare provider first. Abruptly discontinuing the medication can cause a 'rebound' effect, where your body retains fluid even more aggressively than before, leading to rapid weight gain, severe swelling, and potential shortness of breath. If the medication needs to be stopped due to side effects or a change in treatment, your doctor will provide a plan to gradually reduce your dose. This tapering process allows your body and kidneys to adjust safely to the change.
If you miss a dose of Furosemide, take it as soon as you remember. However, if it is already late in the day or close to the time for your next dose, skip the missed dose and return to your regular schedule. Taking Furosemide too late in the evening can cause you to wake up multiple times during the night to urinate, which disrupts sleep. Never take two doses at once to make up for a missed one, as this can lead to severe dehydration or a dangerous drop in blood pressure.
Furosemide is actually expected to cause weight loss, but specifically in the form of 'water weight.' Because it removes excess fluid from the body, patients with edema often see a decrease of several pounds as the swelling subsides. If you experience sudden weight gain while taking Furosemide, it is usually a sign that the medication is not working effectively or that your underlying condition (like heart failure) is worsening. You should report any weight gain of more than 2-3 pounds in a single day to your doctor immediately.
Furosemide interacts with many other drugs, so it is vital to provide your doctor with a full list of everything you take. It can have serious interactions with lithium, digoxin, and certain antibiotics like gentamicin. Common over-the-counter pain relievers, such as ibuprofen (Advil) or naproxen (Aleve), can reduce the effectiveness of Furosemide and increase the risk of kidney damage. Your doctor may need to adjust your dosages or monitor your blood work more frequently if you are taking multiple medications for heart or blood pressure issues.
Yes, Furosemide is widely available as a generic medication and is generally very affordable. The brand name version most people recognize is Lasix. Generic Furosemide is required by the FDA to have the same active ingredient, strength, dosage form, and route of administration as the brand-name drug. It must also prove to be bioequivalent, meaning it works in the body in the same way and over the same amount of time. Choosing the generic version is a safe and cost-effective way to manage your condition.