Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
FUROSEMIDE vs ETHACRYNIC ACID
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Furosemide is a loop diuretic that inhibits the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle, reducing reabsorption of sodium, chloride, and potassium ions, leading to increased urine output.
Inhibits sodium-potassium-chloride cotransporter (NKCC2) in the thick ascending limb of the loop of Henle, leading to increased excretion of sodium, chloride, potassium, and water. Also inhibits prostaglandin degradation.
Edema associated with heart failure, cirrhosis, renal disease,Hypertension,Hypercalcemia (off-label)
Treatment of edema associated with congestive heart failure, cirrhosis, and renal disease,Treatment of ascites,Treatment of hypertension (off-label),Adjunctive therapy in acute pulmonary edema (off-label)
Adults: 20-80 mg orally once or twice daily; IV/IM: 20-40 mg once or twice daily, may increase by 20-40 mg every 6-8 hours. Max dose: 600 mg/day.
50 to 100 mg orally once daily; may increase by 25 to 50 mg increments at intervals of 2 to 3 days up to 400 mg/day. IV: 0.5 to 1 mg/kg slowly (over several minutes); usual initial dose 50 mg.
0.5-2 hours (terminal); prolonged in renal impairment (up to 9-24 hours) and hepatic cirrhosis (up to 2-4 hours).
Terminal elimination half-life is approximately 2-4 hours in patients with normal renal function; may be prolonged in renal impairment.
Furosemide is primarily metabolized via glucuronidation (by UGT1A1, UGT1A9) and to a lesser extent by CYP450 enzymes (minor).
Primarily metabolized by conjugation with glutathione; also undergoes hepatic metabolism via CYP450 enzymes (minor).
Renal (50-80% unchanged; remainder as glucuronide metabolite); fecal (<2%).
Primarily renal (approximately 60-70% as unchanged drug and metabolites) with some biliary/fecal excretion (approximately 30-40%).
91-99% (primarily to albumin).
Approximately 90-98% bound to plasma proteins, primarily albumin.
0.1-0.2 L/kg; increased in neonates (0.2-0.4 L/kg) and disease states (e.g., heart failure, cirrhosis).
Volume of distribution is approximately 0.1-0.2 L/kg, indicating limited extravascular distribution.
Oral: 50-60% (variable, 10-100% range due to food and formulation); IM: 100% (relative to IV).
Oral bioavailability is approximately 100%.
GFR 10-50 m L/min: dose unchanged; GFR <10 m L/min: avoid use or use with caution; anuric patients: contraindicated.
e GFR 30-59 m L/min: no adjustment; e GFR <30 m L/min: avoid use due to risk of ototoxicity and decreased efficacy.
Child-Pugh A-B: no adjustment; Child-Pugh C: reduce dose by 50% and monitor response; increased risk of hypokalemia and volume depletion.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use.
Oral: 1-2 mg/kg/dose every 6-12 hours; IV/IM: 1 mg/kg/dose every 6-12 hours; max dose: 6 mg/kg/dose. Not recommended in neonates unless critical.
Oral: 1 mg/kg/dose once daily; may increase by 1 mg/kg/dose at intervals of 2-3 days up to 3 mg/kg/day. IV: 1 mg/kg/dose slow IV; maximum 50 mg/dose.
Start at lowest effective dose (e.g., 20 mg orally once daily); monitor electrolytes, renal function, and volume status closely; avoid excessive diuresis.
Initiate at lower doses (25 mg orally once daily) due to increased risk of electrolyte disturbances and renal impairment; monitor closely.
Furosemide is a potent diuretic; excessive diuresis may lead to profound electrolyte depletion, volume depletion, and circulatory collapse.
This drug is a potent diuretic which, if given in excessive amounts, can lead to profound diuresis with water and electrolyte depletion. Close medical supervision and dose adjustment are required.
Monitor for electrolyte imbalances (hypokalemia, hyponatremia, hypomagnesemia),Risk of ototoxicity, especially with rapid infusion or concurrent use of other ototoxic drugs,Monitor renal function and blood pressure; caution in patients with severe hepatic cirrhosis or renal impairment,May cause photosensitivity, blood dyscrasias, and hypersensitivity reactions
Risk of excessive diuresis leading to dehydration, electrolyte imbalance, and hypovolemia,May cause ototoxicity, especially with rapid IV administration or in patients with renal impairment,Can worsen azotemia or precipitate hepatic encephalopathy in cirrhotic patients,Monitor serum electrolytes, CO2, BUN, and creatinine regularly,Use with caution in patients with diabetes mellitus (may increase blood glucose),May cause hyperuricemia and gout
Anuria,Severe electrolyte depletion,Hypersensitivity to furosemide or sulfonamides,Hepatic coma or precoma (relative)
Anuria,Hypersensitivity to ethacrynic acid or any component of the formulation,Severe electrolyte depletion (hypokalemia, hyponatremia) until corrected,Concurrent use with other ototoxic drugs (e.g., aminoglycosides) may increase risk
Avoid excessive salt intake to prevent fluid retention and counteract diuretic effect. Limit alcohol as it can increase diuretic effect and cause dehydration. May increase potassium loss; consider potassium-rich foods (bananas, oranges, spinach) unless contraindicated (e.g., with ACE inhibitors). No specific restrictions with grapefruit juice.
Avoid licorice, which can worsen hypokalemia. Limit salt intake as directed. No specific food interactions; maintain a balanced diet.
Furosemide is pregnancy category C. First trimester: Limited human data; animal studies show no teratogenicity at clinically relevant doses, but fetal toxicity (hydronephrosis) at high doses. Second/third trimesters: Risk of electrolyte imbalance in mother and fetus, potential for decreased placental perfusion due to maternal hypovolemia. Use only if benefit outweighs risk, especially in oligohydramnios or preeclampsia.
First trimester: Limited human data; animal studies show no teratogenicity but fetal toxicity at high doses. Second trimester: Theoretical risk of electrolyte imbalances affecting fetal development. Third trimester: Risk of premature ductus arteriosus closure due to prostaglandin inhibition (theoretical), neonatal ototoxicity, and thrombocytopenia.
Furosemide is excreted into breast milk in low amounts (M/P ratio approximately 2.6). Theoretical risk of electrolyte imbalance in infant. Consider using lowest effective dose and monitor infant for signs of dehydration or electrolyte disturbances.
Safety not established. Drug excreted in breast milk; M/P ratio unknown. Avoid breastfeeding or use with caution due to potential for ototoxicity and electrolyte disturbances in the infant.
Pregnancy increases renal clearance and volume of distribution, potentially reducing plasma furosemide levels, but dosing adjustments are not routinely recommended due to risk of hypovolemia. Use lowest effective dose and titrate based on response, with close monitoring.
No standard dose adjustment; use lowest effective dose. Monitor for hypokalemia and volume depletion, which may be more pronounced in pregnancy. Consider adjusting dose based on maternal weight and renal function.
Monitor urine output and electrolytes, especially potassium. Avoid use in anuria, severe electrolyte depletion, and hepatic coma. Can cause ototoxicity, especially with rapid IV administration or concurrent use of other ototoxic drugs. Sulfonamide allergy may cross-react; use caution. Loop diuretics like furosemide are effective in renal impairment, unlike thiazides.
Ethacrynic acid is a loop diuretic used for patients with sulfonamide allergy, as it is not a sulfonamide derivative. Monitor for ototoxicity, especially when given with aminoglycosides or in renal impairment. Rapid diuresis may cause hypokalemia, hypomagnesemia, and metabolic alkalosis. Use cautiously in hepatic cirrhosis to avoid electrolyte-induced coma.
Take exactly as prescribed, preferably in the morning to avoid nighttime urination.,Weigh yourself daily and report rapid weight gain or loss.,Avoid alcohol and NSAIDs as they may reduce diuretic effect or increase kidney damage.,Report hearing loss, ringing in ears, dizziness, or muscle cramps immediately.,Do not stop suddenly without consulting your doctor; may cause rebound edema.,Limit high-potassium foods if also taking ACE inhibitors or potassium-sparing diuretics.,Stay hydrated but avoid excessive fluid intake.
Take exactly as prescribed, usually once or twice daily.,Expect increased urination; take in the morning to avoid nighttime trips.,Weigh yourself daily and report rapid weight gain or loss.,Avoid alcohol and medications that may cause dizziness.,This drug may cause hearing loss or ringing in the ears; report immediately.,Do not take with aspirin or other NSAIDs without doctor approval.,Inform your doctor if you have gout, diabetes, or kidney disease.,Stay adequately hydrated but avoid excessive fluid intake.
"Alfentanil, a potent opioid analgesic, can cause significant hypotension and respiratory depression. When combined with furosemide, a loop diuretic that reduces blood volume and vascular resistance, there is a synergistic decrease in blood pressure, which may precipitate cardiovascular collapse, especially in patients with compromised circulatory reserves. Additionally, furosemide may enhance the sedative and respiratory depressant effects of alfentanil, leading to increased risk of respiratory acidosis and altered mental status."
"Zaltoprofen, a nonsteroidal anti-inflammatory drug (NSAID), reduces the antihypertensive and diuretic efficacy of furosemide by inhibiting renal prostaglandin synthesis. This blockade diminishes renal blood flow and natriuretic response, potentially leading to fluid retention and diminished blood pressure control. The interaction may precipitate or exacerbate heart failure and edema in susceptible patients."
"Isoflurane, a halogenated inhalational anesthetic, can cause dose-dependent myocardial depression and systemic vasodilation, leading to decreased blood pressure and renal perfusion. Furosemide, a loop diuretic, further reduces intravascular volume and renal blood flow via inhibition of the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle. Co-administration may result in additive hypotension, acute kidney injury, and electrolyte imbalances (e.g., hypokalemia, hypomagnesemia), particularly in patients with pre-existing renal impairment or hemodynamic instability."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about FUROSEMIDE vs ETHACRYNIC ACID, answered by our medical review team.
FUROSEMIDE is a Loop Diuretic that works by Furosemide is a loop diuretic that inhibits the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle, reducing reabsorption of sodium, chloride, and potassium ions, leading to increased urine output.. ETHACRYNIC ACID is a Loop Diuretic that works by Inhibits sodium-potassium-chloride cotransporter (NKCC2) in the thick ascending limb of the loop of Henle, leading to increased excretion of sodium, chloride, potassium, and water. Also inhibits prostaglandin degradation.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between FUROSEMIDE and ETHACRYNIC ACID depend on the specific clinical indication. These are both Loop Diuretic agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of FUROSEMIDE is: Adults: 20-80 mg orally once or twice daily; IV/IM: 20-40 mg once or twice daily, may increase by 20-40 mg every 6-8 hours. Max dose: 600 mg/day.. The standard adult dose of ETHACRYNIC ACID is: 50 to 100 mg orally once daily; may increase by 25 to 50 mg increments at intervals of 2 to 3 days up to 400 mg/day. IV: 0.5 to 1 mg/kg slowly (over several minutes); usual initial dose 50 mg.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between FUROSEMIDE and ETHACRYNIC ACID in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. FUROSEMIDE is classified as Category A/B. Furosemide is pregnancy category C. First trimester: Limited human data; animal studies show no teratogenicity at clinically relevant doses, but fetal toxicity (hydronephrosis) at . ETHACRYNIC ACID is classified as Category C. First trimester: Limited human data; animal studies show no teratogenicity but fetal toxicity at high doses. Second trimester: Theoretical risk of electrolyte imbalances affecting . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.