Brand name: Lasix
Drug class: Loop Diuretics

Medically reviewed by Drugs.com on Jan 10, 2025. Written by ASHP.

Introduction

A sulfonamide, loop-type diuretic and antihypertensive agent.

Uses for Furosemide

Edema

Management of edema associated with heart failure, hepatic cirrhosis, and renal disease (e.g., nephrotic syndrome).

Considered a diuretic of choice for most patients with heart failure.

Most experts state that all patients with symptomatic heart failure who have evidence for, or a history of, fluid retention generally should receive diuretic therapy in conjunction with moderate sodium restriction, an agent to inhibit the renin-angiotensin-aldosterone (RAA) system (e.g., ACE inhibitor, angiotensin II receptor antagonist, angiotensin receptor-neprilysin inhibitor [ARNI]), a β-adrenergic blocking agent (β-blocker), and in selected patients, an aldosterone antagonist.

IV management of acute pulmonary edema (in combination with oxygen and a cardiac glycoside).

Hypertension

Management of hypertension, alone or in combination with other classes of antihypertensive agents.

Not considered a preferred agent for initial management of hypertension according to current evidence-based hypertension guidelines; other agents (i.e., ACE inhibitors, angiotensin II receptor antagonists, calcium-channel blockers, thiazide diuretics) are preferred for initial management.

Some experts state that loop diuretics (e.g., bumetanide, furosemide, torsemide) are preferred over thiazides in patients with moderate to severe chronic kidney disease (CKD) or symptomatic heart failure.

Individualize choice of therapy; consider patient characteristics (e.g., age, ethnicity/race, comorbidities, cardiovascular risk) as well as drug-related factors (e.g., ease of administration, availability, adverse effects, cost).

A 2017 ACC/AHA multidisciplinary hypertension guideline classifies BP in adults into 4 categories: normal, elevated, stage 1 hypertension, and stage 2 hypertension. (See Table 1.)

Source: Whelton PK, Carey RM, Aronow WS et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Hypertension. 2018;71:e13-115.

Individuals with SBP and DBP in 2 different categories (e.g., elevated SBP and normal DBP) should be designated as being in the higher BP category (i.e., elevated BP).

The goal of hypertension management and prevention is to achieve and maintain optimal control of BP. However, the BP thresholds used to define hypertension, the optimum BP threshold at which to initiate antihypertensive drug therapy, and the ideal target BP values remain controversial.

The 2017 ACC/AHA hypertension guideline generally recommends a target BP goal (i.e., BP to achieve with drug therapy and/or nonpharmacologic intervention) of <130/80 mm Hg in all adults regardless of comorbidities or level of atherosclerotic cardiovascular disease (ASCVD) risk. In addition, an SBP goal of <130 mm Hg generally is recommended for noninstitutionalized ambulatory patients ≥65 years of age with an average SBP of ≥130 mm Hg. These BP goals are based upon clinical studies demonstrating continuing reduction of cardiovascular risk at progressively lower levels of SBP.

Other hypertension guidelines generally have based target BP goals on age and comorbidities. Guidelines such as those issued by the JNC 8 expert panel generally have targeted a BP goal of <140/90 mm Hg regardless of cardiovascular risk, and have used higher BP thresholds and target BPs in elderly patients compared with those recommended by the 2017 ACC/AHA hypertension guideline.

Some clinicians continue to support previous target BPs such as those recommended by JNC 8 due to concerns about the lack of generalizability of data from some clinical trials (e.g., SPRINT study) used to support the 2017 ACC/AHA hypertension guideline and potential harms (e.g., adverse drug effects, costs of therapy) versus benefits of BP lowering in patients at lower risk of cardiovascular disease.

Consider potential benefits of hypertension management and drug cost, adverse effects, and risks associated with the use of multiple antihypertensive drugs when deciding a patient's BP treatment goal.

For decisions regarding when to initiate drug therapy (BP threshold), the 2017 ACC/AHA hypertension guideline incorporates underlying cardiovascular risk factors. ASCVD risk assessment is recommended by ACC/AHA for all adults with hypertension.

ACC/AHA currently recommend initiation of antihypertensive drug therapy in addition to lifestyle/behavioral modifications at an SBP ≥140 mm Hg or DBP ≥90 mm Hg in adults who have no history of cardiovascular disease (i.e., primary prevention) and a low ASCVD risk (10-year risk <10%).

For secondary prevention in adults with known cardiovascular disease or for primary prevention in those at higher risk for ASCVD (10-year risk ≥10%), ACC/AHA recommend initiation of antihypertensive drug therapy at an average SBP ≥130 mm Hg or an average DBP ≥80 mm Hg.

Adults with hypertension and diabetes mellitus, CKD, or age ≥65 years are assumed to be at high risk for cardiovascular disease; ACC/AHA state that such patients should have antihypertensive drug therapy initiated at a BP ≥130/80 mm Hg. Individualize drug therapy in patients with hypertension and underlying cardiovascular or other risk factors.

In stage 1 hypertension, experts state that it is reasonable to initiate drug therapy using the stepped-care approach in which one drug is initiated and titrated and other drugs are added sequentially to achieve the target BP. Initiation of antihypertensive therapy with 2 first-line agents from different pharmacologic classes recommended in adults with stage 2 hypertension and average BP >20/10 mm Hg above BP goal.

Furosemide Dosage and Administration

General

Edema

• Careful etiologic diagnosis should precede the use of any diuretic.

• Hospitalization of the patient during initiation of therapy is advisable, especially for patients with hepatic cirrhosis and ascites or chronic renal failure.

• In prolonged diuretic therapy, intermittent use of the drug (e.g., on 2–4 consecutive days each week) may be advisable.

• For the management of fluid retention (e.g., edema) associated with heart failure, experts state that diuretics should be administered at a dosage sufficient to achieve optimal volume status and relieve congestion without inducing an excessively rapid reduction in intravascular volume, which could result in hypotension, renal dysfunction, or both.

Monitoring and BP Treatment Goals

• Monitor BP regularly (i.e., monthly) during therapy and adjust dosage of the antihypertensive drug until BP controlled.

• If added to regimen of a patient receiving another antihypertensive agent, reduce dosage of preexisting therapy by ≥50% initially to avoid severe hypotension; additional dosage adjustment may be required.

• If unacceptable adverse effects occur, discontinue drug and initiate another antihypertensive agent from a different pharmacologic class.

• Assess patient's renal function and electrolytes 2–4 weeks after initiation of diuretic therapy.

• If adequate BP response not achieved with a single antihypertensive agent, either increase dosage of single drug or add a second drug with demonstrated benefit and preferably a complementary mechanism of action (e.g., ACE inhibitor, angiotensin II receptor antagonist, calcium-channel blocker). Many patients will require ≥2 drugs from different pharmacologic classes to achieve BP goal; if goal BP still not achieved with 2 antihypertensive agents, add a third drug.

Administration

Administer orally, IV, or IM.

Oral Administration

Administer orally once (preferably in the morning) or twice daily.

For ease of administration and maximum dosage flexibility in children, consider use of oral solution preparation.

IV Administration

IV administration may be used in emergency clinical circumstances when a rapid onset of diuresis is desired, or in patients unable to take oral medication or those with impaired GI absorption; replace with oral therapy as soon as possible.

Consider the potential risks, when using large parenteral doses; monitor patient closely.

Dilution

For IV infusion, dilute in 5% dextrose, 0.9% sodium chloride, or lactated Ringer’s injection and adjust pH to >5.5.

Rate of Administration

For direct IV injection, administer slowly over a period of 1–2 minutes.

If high-dose parenteral furosemide therapy is necessary, the manufacturer recommends that the drug be administered as a controlled infusion at a rate not exceeding 4 mg/minute in adults.

Standardize 4 Safety

Standardized concentrations for IV furosemide have been established through Standardize 4 Safety (S4S), a national patient safety initiative to reduce medication errors, especially during transitions of care. Because recommendations from the S4S panels may differ from the manufacturer’s prescribing information, caution is advised when using concentrations that differ from labeling, particularly when using rate information from the label. For additional information on S4S (including updates that may be available), see [Web] .

Dosage

Individualize dosage according to patient’s requirements and response; titrate dosage to gain maximum therapeutic effect while using the lowest possible effective dosage. (See Boxed Warning.)

Pediatric Patients

Edema

Oral

2 mg/kg administered as a single dose. If necessary, increase in increments of 1 or 2 mg/kg every 6–8 hours to a maximum of 6 mg/kg. Generally not necessary to exceed individual doses of 4 mg/kg or a dosing frequency of once or twice daily. Use minimum effective dosage for maintenance therapy.

IV or IM

1 mg/kg administered as a single IM or IV injection. If necessary for resistant forms of edema, the initial dose may be increased by 1 mg/kg no more often than every 2 hours until the desired effect has been obtained or up to a maximum dosage of 6 mg/kg. Adequate response usually is obtained with individual parenteral doses of 1 mg/kg.

Acute Pulmonary Edema

IV or IM

1 mg/kg administered as a single IM or IV injection. If necessary for resistant forms of edema, the initial dose may be increased by 1 mg/kg no more often than every 2 hours until the desired effect has been obtained or up to a maximum dosage of 6 mg/kg. Adequate response generally obtained with 1 mg/kg.

Hypertension† [off-label]

Oral

Initially, 0.5–2 mg/kg given once or twice daily. Increase as necessary up to a maximum of 6 mg/kg daily.

Adults

Edema

Oral

20–80 mg given as a single dose, preferably in the morning. If needed, repeat same dose 6–8 hours later or increase dose by 20- to 40-mg increments and give no sooner than 6–8 hours after last dose until desired diuretic response (including weight loss) is obtained. May titrate carefully up to 600 mg daily in severe cases.

The effective dose may be given once or twice daily thereafter, or, in some cases, by intermittent administration on 2–4 consecutive days each week. Dosage may be reduced for maintenance therapy.

For management of fluid retention (e.g., edema) associated with heart failure, some experts recommend initiating furosemide at a low dosage (e.g., 20–40 mg once or twice daily) and increasing dosage (maximum 600 mg daily) until urine output increases and weight decreases, generally by 0.5–1 kg daily.

IV or IM

20–40 mg given as a single IM or IV injection. If needed, repeat same dose 2 hours later or increase dose by 20-mg increments and give no sooner than every 2 hours until the desired diuretic response is obtained. Effective dosages may then be given once or twice daily.

Acute Pulmonary Edema

IV

40 mg given as a single IV injection. If needed, an 80-mg dose may be given 1 hour after the initial dose.

Hypertension

Oral

40 mg twice daily. If desired BP not attained, consider adding other antihypertensive agents.

Some experts state that usual dosage range is 20–80 mg daily in 2 divided doses.

Prescribing Limits

Pediatric Patients

Edema

Oral

Maximum of 6 mg/kg.

IV or IM

Maximum of 6 mg/kg in infants and children; do not exceed 1 mg/kg daily in premature infants.

Hypertension† [off-label]

Oral

Maximum 6 mg/kg daily.

Adults

Edema

Oral

Maximum of 600 mg daily.

Special Populations

Renal Impairment

Higher doses may be required for patients with acute or chronic renal failure.

Cautions for Furosemide

Contraindications

• Anuria.

• Known hypersensitivity to furosemide or any ingredient in the formulation.

Warnings/Precautions

Warnings

Hepatic Effects

Sudden alterations of electrolyte balance in patients with cirrhosis may precipitate hepatic coma; use with caution in patients with hepatic cirrhosis and ascites.

Do not initiate therapy in patients with hepatic coma or electrolyte depletion until the basic condition is improved. Therapy in such patients is best initiated in the hospital with careful monitoring of clinical status and electrolyte balance.

Renal Effects

If increasing azotemia and oliguria occur during treatment of severe progressive renal disease, discontinue the drug.

Sensitivity Reactions

Anaphylaxis

Anaphylaxis (e.g., urticaria, angioedema, hypotension) within 5 minutes after IV administration reported.

Systemic Lupus Erythematosus

Possible exacerbation or activation of systemic lupus erythematosus.

Sulfonamide Sensitivity

Patients sensitive to sulfonamides may show allergic reactions to furosemide.

Photosensitivity

Photosensitivity may occur.

Major Toxicities

Ototoxicity

Risk of tinnitus, reversible or permanent hearing impairment increased following IV or IM administration, especially at high dosages, after too-rapid administration, in patients with severely impaired renal function, and/or in patients receiving other ototoxic drugs (e.g., aminoglycosides). (See Specific Drugs under Interactions.)

If high-dose IV therapy is indicated, administer by slow IV infusion (e.g., at a rate not exceeding 4 mg/minute in adults).

General Precautions

Fluid, Electrolyte, and Cardiovascular Effects

Excessive diuresis may cause dehydration and blood volume reduction with circulatory collapse and possibly vascular thrombosis and embolism, particularly in elderly patients. (See Boxed Warning.)

Risk of orthostatic hypotension, especially with brisk diuresis. May be aggravated by concomitant use with alcohol, barbiturates, or narcotics.

Risk of hypokalemia, especially with brisk diuresis, inadequate oral electrolyte intake, when cirrhosis is present, or during concomitant use of corticosteroids or ACTH. Concomitant therapy with digitalis may exaggerate metabolic effects of hypokalemia, especially myocardial effects.

Observe carefully for manifestations of fluid and electrolyte depletion (e.g., dryness of mouth, thirst, weakness, lethargy, drowsiness, restlessness, muscle pains or cramps, muscular fatigue, hypotension, oliguria, tachycardia, arrhythmia, nausea, vomiting).

Endocrine Effects

Possible increased blood glucose and alterations in glucose tolerance tests (with abnormalities of the fasting and 2-hour postprandial sugar); precipitation of diabetes mellitus rarely reported. Monitor urine and blood glucose concentrations periodically in patients with diabetes and those suspected of latent diabetes.

Possible hyperuricemia and precipitation of gout; use with caution in patients with a history of gout or elevated serum uric acid concentrations.

Patient Monitoring

Monitor regularly for the possible occurrence of blood dyscrasias, liver or kidney damage, or other idiosyncratic reactions.

Serum electrolytes (particularly potassium), CO₂, S_cr, and BUN should be determined frequently during the first few months of therapy and periodically thereafter.

Elective Surgery

Discontinue therapy 1 week (oral furosemide) or 2 days (parenteral furosemide) before elective surgery.

Specific Populations

Pregnancy

Category C.

Lactation

Distributed into milk. Use with caution.

Pediatric Use

Risk of persistent patent ductus arteriosus (PDA) may be increased in premature neonates with respiratory distress syndrome (RDS) who receive furosemide during the first weeks of life.

Do not exceed dosage of 1 mg/kg per 24 hours in premature neonates with <31 weeks’ postconception age (gestational age at birth plus postnatal age); risk of potentially toxic furosemide plasma concentrations with higher dosages.

Renal calcification reported in severely premature infants treated with IV furosemide for edema due to PDA and hyaline membrane disease; concomitant chlorothiazide therapy may decrease hypercalciuria and dissolve some calculi.

Hearing loss reported in neonates; possibly secondary to renal immaturity.

Oral solutions contain sorbitol; high dosages may cause diarrhea in children.

Hepatic Impairment

Use with caution.

Renal Impairment

Use with caution.

Common Adverse Effects

Orthostatic hypotension, dizziness, electrolyte imbalance (hyponatremia, hypokalemia, hypochloremia) tinnitus, photosensitivity.

Drug Interactions

Specific Drugs

Furosemide Pharmacokinetics

Absorption

Bioavailability

Mean oral bioavailability of furosemide from commercially available tablets and oral solution is 64% and 60%, respectively.

Commercially available tablets and oral solution are bioequivalent.

Onset

Following oral administration, onset of diuresis occurs within 30 minutes to 1 hour; maximal effect after 1–2 hours.

Following IV administration, diuresis occurs within 5 minutes and peaks within 20–60 minutes.

Onset of diuresis after IM administration occurs somewhat later than after IV administration.

Maximum hypotensive effect may not be apparent until after several days of therapy.

Duration

Diuretic effect persists 6–8 hours following oral administration and approximately 2 hours following IV administration.

Food

Food does not appear to affect diuretic effect.

Special Populations

In patients with severely impaired renal function, the diuretic response may be prolonged.

Distribution

Extent

Crosses the placenta and is distributed into milk.

Plasma Protein Binding

Approximately 95% bound to plasma proteins (mainly albumin) in both normal and azotemic patients.

Elimination

Metabolism

Metabolized in the liver to the defurfurylated derivative, 4-chloro-5-sulfamoylanthranilic acid.

Elimination Route

Rapidly excreted in urine by glomerular filtration and by secretion from the proximal tubule.

Approximately 50% of an oral dose and 80% of an IV or IM dose are excreted in urine within 24 hours; 69–97% of these amounts is excreted in the first 4 hours. The remainder of the drug is eliminated by nonrenal mechanisms including degradation in the liver and excretion of unchanged drug in the feces.

Half-life

Biphasic; terminal half-life is approximately 2 hours.

Special Populations

Hepatic or renal impairment prolongs the elimination half-life of the drug.

In patients with marked renal impairment without liver disease, nonrenal clearance is increased to the extent that up to 98% of the drug is cleared within 24 hours.

Not removed by hemodialysis.

Stability

Storage

Oral

Solution or Tablets

Tight, light resistant containers at 15–30°C.

Parenteral

Injection

15–30°C; protect from light. Discard unused portion.

Actions

• Inhibits primarily the absorption of sodium and chloride not only in the proximal and distal tubules but also in the ascending limb of the loop of Henle. Does not inhibit carbonic anhydrase and is not an aldosterone antagonist.

• Mechanism of hypotensive effect not definitively determined but presumed to result from decreased plasma volume.

• Induces greater diuresis and electrolyte loss than with thiazides or most other diuretics except ethacrynic acid.

• Possesses some renal vasodilator effect; renal vascular resistance decreases and renal blood flow increases following administration.

Advice to Patients

• Risks associated with excessive fluid loss or electrolyte imbalance.

• Potential for postural hypotension; importance of rising slowly from a seated position.

• Importance of discussing dietary measures and supplementation to prevent or correct hypokalemia.

• Importance of informing patients with diabetes mellitus that blood glucose and urine glucose concentrations may increase.

• Importance of informing patients of possible photosensitivity.

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs (e.g., appetite suppressants, cold remedies) as well as any concomitant illnesses.

• Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.

• Importance of informing patients of other important precautionary information. (See Cautions.)

Additional Information

The American Society of Health-System Pharmacists, Inc. represents that the information provided in the accompanying monograph was formulated with a reasonable standard of care, and in conformity with professional standards in the field. Readers are advised that decisions regarding use of drugs are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and that the information contained in the monograph is provided for informational purposes only. The manufacturer’s labeling should be consulted for more detailed information. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information contained in the monograph is not a substitute for medical care.

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

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Frequently asked questions

• What are the equivalent dosages of bumetanide, furosemide & torsemide?

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