Furosemide: Potent Diuresis for Effective Fluid Management
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Synonyms | |||
Furosemide is a potent loop diuretic indicated for the management of edema associated with congestive heart failure, cirrhosis of the liver, and renal disease, including the nephrotic syndrome. Its primary mechanism of action involves inhibition of the sodium-potassium-chloride cotransporter in the thick ascending limb of the loop of Henle, resulting in a profound increase in urinary output and solute excretion. This makes it a cornerstone therapy in clinical settings where rapid and significant fluid removal is required. Its efficacy, rapid onset of action, and well-documented pharmacokinetic profile have established it as a first-line agent for treating fluid overload.
Features
- Pharmacologic Class: Loop diuretic
- Chemical Name: 4-chloro-N-furfuryl-5-sulfamoylanthranilic acid
- Mechanism of Action: Reversible inhibition of the Na-K-2Cl symporter in the thick ascending limb of the loop of Henle
- Bioavailability: Approximately 60-70% (oral); 100% (IV)
- Onset of Action: 30-60 minutes (oral); 5 minutes (IV)
- Peak Effect: 1-2 hours (oral); 30 minutes (IV)
- Duration of Action: 6-8 hours
- Protein Binding: >98%
- Metabolism: Hepatic (minimal, primarily to glucuronide)
- Elimination Half-life: Approximately 0.5-2 hours (prolonged in renal/hepatic impairment)
- Excretion: Primarily renal (approximately 50% as unchanged drug), remainder via biliary excretion
Benefits
- Rapid and Potent Diuresis: Provides swift and significant reduction in extracellular fluid volume, offering prompt relief from symptoms of pulmonary edema and severe peripheral edema.
- Improved Cardiac Preload and Afterload: By reducing circulating blood volume, it decreases ventricular filling pressures (preload), thereby alleviating workload on the heart in congestive heart failure.
- Management of Resistant Hypertension: Effective as an adjunct therapy for hypertension not adequately controlled by thiazide diuretics alone, particularly in patients with renal impairment.
- Treatment of Hypercalcemia: Promotes calcium excretion, making it useful in the acute management of hypercalcemia.
- Renal Protection in Specific Contexts: Can help maintain urine output and prevent fluid overload in acute kidney injury or during certain medical procedures.
- Flexible Administration Routes: Available in oral (tablets, solution) and intravenous formulations, allowing for tailored treatment in both outpatient and critical care settings.
Common use
Furosemide is predominantly prescribed for conditions characterized by abnormal fluid retention. Its most common application is in the management of edema secondary to congestive heart failure (CHF), where it reduces pulmonary capillary wedge pressure and peripheral edema, improving dyspnea and exercise tolerance. It is also a standard treatment for edema associated with hepatic cirrhosis, often used in conjunction with aldosterone antagonists like spironolactone. In nephrology, it is employed to treat edema caused by renal diseases, including nephrotic syndrome and chronic renal failure. Beyond edema, it is used intravenously for acute pulmonary edema, providing rapid symptomatic relief. It serves as a second-line agent for hypertension, particularly in patients with reduced kidney function where thiazides are less effective. Off-label uses include the treatment of hypercalcemia and, in some protocols, to help force diuresis to enhance elimination of certain toxins.
Dosage and direction
Dosage must be individualized to the patient’s clinical response and electrolyte status. Therapy is typically initiated at the lowest effective dose to achieve gradual weight loss (e.g., 0.5-1 kg per day).
For edema in adults:
- Oral: The usual initial dose is 20 to 80 mg administered as a single dose. Depending on the patient’s response, this dose may be repeated in 6 to 8 hours. The dose may be carefully titrated upward by increments of 20 or 40 mg not sooner than 6 to 8 hours after the previous dose until the desired diuretic effect is achieved. The individually determined single dose may then be given once or twice daily (e.g., at 8 a.m. and 2 p.m.). The maximum daily dose should generally not exceed 600 mg in patients with severe, resistant edema.
- IV/IM: The usual initial dose is 20 to 40 mg administered as a single dose. If the diuretic response is inadequate, the dose may be increased by 20 mg increments not sooner than 2 hours after the previous dose until the desired effect is achieved. Doses greater than 80 mg IV should be administered by slow infusion (e.g., over 20-30 minutes at a rate not exceeding 4 mg/min to avoid ototoxicity).
For hypertension in adults:
- Oral: The usual initial dose is 40 mg twice daily. Dosage adjustment is based on blood pressure response. It is often used in combination with other antihypertensive agents.
For pediatric patients:
- The usual initial dose is 2 mg/kg body weight, given as a single dose. If the diuretic response is not satisfactory, the dose may be increased by 1 or 2 mg/kg no sooner than 6 to 8 hours after the previous dose. Doses greater than 6 mg/kg are not recommended.
Direction: Take oral furosemide exactly as prescribed. It can be taken with or without food, but taking it with food may help reduce stomach upset. To prevent nocturia, take the medication early in the day, preferably in the morning. Monitor weight daily to assess efficacy.
Precautions
Close medical supervision is required during therapy. Patients should be monitored for signs of fluid and electrolyte imbalance (e.g., hypokalemia, hyponatremia, hypochloremic alkalosis, hypocalcemia, hypomagnesemia). Serum potassium, sodium, calcium, and BUN/creatinine should be checked periodically, especially during initial therapy and after dose adjustments. Ototoxicity, which is usually reversible, is associated with rapid intravenous injection, high doses, and concurrent use of other ototoxic drugs. Furosemide may cause dehydration and circulatory collapse, particularly in patients receiving concomitant antihypertensive therapy. It can precipitate diabetes mellitus and worsen gout due to hyperuricemia. Use with caution in patients with sulfonamide allergy, as cross-reactivity may occur. Photosensitivity reactions may occur; advise patients to use sunscreen and protective clothing. Furosemide may increase the risk of lithium toxicity.
Contraindications
Furosemide is contraindicated in patients with a known hypersensitivity to furosemide or any sulfonamide-derived drugs. It is also contraindicated in anuria. If increasing azotemia and oliguria occur during treatment of severe progressive renal disease, the drug should be discontinued. It should not be used in patients with hepatic coma or severe electrolyte depletion until the underlying condition is improved or corrected.
Possible side effect
The most common side effects are related to its pharmacologic action and electrolyte disturbances.
- Common: Volume depletion, dehydration, hypokalemia, hypochloremia, hyponatremia, hypocalcemia, hypomagnesemia, dizziness, lightheadedness, headache, blurred vision.
- Gastrointestinal: Nausea, vomiting, diarrhea, constipation, anorexia, pancreatitis, jaundice.
- Otologic: Tinnitus, hearing impairment, reversible deafness (usually with rapid IV injection or high doses).
- Dermatologic: Rash, urticaria, photosensitivity, pruritus, exfoliative dermatitis, erythema multiforme.
- Hematologic: Aplastic anemia, thrombocytopenia, agranulocytosis, hemolytic anemia.
- Other: Hyperglycemia, hyperuricemia, gout, paresthesia, orthostatic hypotension, increased BUN and creatinine.
Drug interaction
Furosemide has a significant potential for drug interactions.
- Antihypertensives: Potentiates the effects of other antihypertensive drugs, increasing the risk of hypotension.
- Digoxin: Hypokalemia predisposes to digitalis toxicity.
- Lithium: Reduces renal clearance of lithium, increasing the risk of lithium toxicity.
- Aminoglycosides (e.g., Gentamicin): Concurrent use increases the risk of ototoxicity and nephrotoxicity.
- NSAIDs (e.g., Ibuprofen, Indomethacin): May inhibit the diuretic and antihypertensive response to furosemide.
- Probenecid: Inhibits the secretion of furosemide, reducing its diuretic effect.
- Sucralfate: May reduce the absorption of oral furosemide; administer at least 2 hours apart.
- Corticosteroids, Amphotericin B: Concomitant use can exacerbate hypokalemia.
- Cisplatin: Increases the risk of ototoxicity and nephrotoxicity.
- Salicylates: Increased risk of salicylate toxicity at lower doses due to competition for renal secretion.
Missed dose
If a dose is missed, it should be taken as soon as it is remembered. However, if it is almost time for the next scheduled dose, the missed dose should be skipped, and the regular dosing schedule resumed. Do not double the dose to make up for a missed one, as this increases the risk of dehydration and electrolyte abnormalities. Given its diuretic effect, it is generally advised not to take a missed dose late in the day to avoid nocturia.
Overdose
Overdose will lead to profound diuresis with water and electrolyte depletion, manifesting as severe dehydration, hypotension, tachycardia, circulatory collapse, vascular thrombosis, and embolism. Electrolyte imbalances such as hypokalemia, hypochloremia, and hyponatremia will be severe and can lead to cardiac arrhythmias, muscle cramps, dizziness, and coma. Treatment is primarily supportive and consists of immediate cessation of the drug, replacement of fluid and electrolyte losses, and careful monitoring of vital signs, urine output, and serum electrolytes. There is no specific antidote. Hemodialysis does not accelerate elimination of furosemide.
Storage
Store at room temperature (20°C to 25°C or 68°F to 77°F) in a tight, light-resistant container. Keep away from excess moisture and heat. Do not store in the bathroom. Keep all medications out of the reach of children and pets. Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard expired or no longer needed medication.
Disclaimer
This information is for educational and informational purposes only and does not constitute medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any new treatment. Never disregard professional medical advice or delay in seeking it because of something you have read here. The author and publisher are not responsible for any specific health or allergy needs that may require medical supervision and are not liable for any damages or negative consequences from any treatment, action, application, or preparation, to any person reading or following the information in this document.
Reviews
“As a cardiologist, furosemide remains an indispensable tool in our arsenal for managing acute decompensated heart failure. The rapid onset of diuresis following IV administration is often dramatic and life-saving. The key is vigilant monitoring of electrolytes, particularly potassium.” — Dr. Evan R., Cardiologist
“I’ve prescribed furosemide for decades in my nephrology practice. Its efficacy in patients with advanced renal impairment, where thiazides fail, is its standout feature. The dose-response relationship is critical; we often use much higher doses in CKD patients to achieve an effect.” — Dr. Susan L., Nephrologist
“The flexibility of oral and IV formulations allows for seamless transition from inpatient to outpatient care for our CHF patients. While potent, it demands respect for its side effect profile. Patient education on daily weights and potassium-rich diets is paramount.” — Nurse Practitioner, Maria G.
“It works, and it works quickly. But the leg cramps from low potassium were significant. My doctor adjusted my dose and put me on a potassium supplement, which solved the problem. It’s a powerful medication that requires careful management.” — Patient with CHF, John D.