Furosemide is a high-ceiling loop diuretic indicated for the management of edema associated with congestive heart failure, cirrhosis of the liver, and renal disease, including the nephrotic syndrome. It acts on the thick ascending limb of the loop of Henle to inhibit the reabsorption of sodium and chloride, producing a profound diuresis. This agent is particularly valuable in clinical scenarios requiring rapid and significant fluid removal. Its predictable pharmacokinetic profile and established safety record make it a cornerstone therapy in both acute and chronic settings.

Features

• Active Ingredient: Furosemide
• Pharmacologic Class: Loop diuretic
• Available Formulations: Oral tablets (20 mg, 40 mg, 80 mg), intravenous solution (10 mg/mL)
• Mechanism of Action: Inhibits the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle
• Onset of Action: Oral: 30-60 minutes; IV: within 5 minutes
• Peak Effect: Oral: 1-2 hours; IV: 30 minutes
• Duration of Action: 6-8 hours
• Bioavailability: Approximately 50% for oral formulation
• Protein Binding: >98%
• Metabolism: Hepatic (minimal)
• Elimination Half-life: Approximately 2 hours
• Excretion: Primarily renal (unchanged drug)

Benefits

• Rapid and Significant Diuresis: Provides prompt relief from pulmonary edema and peripheral swelling, often within hours of administration.
• Improved Cardiac Output: Reduces preload in heart failure patients, alleviating symptoms of dyspnea and orthopnea.
• Flexible Dosing: Available in multiple strengths and routes of administration, allowing for tailored therapy across various clinical situations.
• Established Safety Profile: Decades of clinical use with well-characterized adverse effect patterns and management strategies.
• Cost-Effective Therapy: Generic availability makes it accessible for long-term management of chronic conditions.
• Predictable Pharmacokinetics: Linear dose-response relationship facilitates dose titration and monitoring.

Common use

Furosemide is primarily employed in the treatment of conditions characterized by fluid overload. Its most frequent application is in the management of edema due to congestive heart failure, where it reduces ventricular filling pressures and improves symptoms. In hepatic cirrhosis with ascites, it is used in combination with spironolactone to mobilize third-space fluid. The drug is also indicated for hypertension, particularly when thiazide diuretics prove insufficient, though this represents a secondary use. In renal impairment, furosemide helps maintain urine output and manage fluid balance, though higher doses may be required due to reduced drug delivery to the nephron.

Dosage and direction

Oral Administration:

• Edema: Initial dose 20-80 mg as a single dose, may repeat in 6-8 hours. Maintenance dose adjusted by 20-40 mg increments at 6-8 hour intervals.
• Hypertension: 40 mg twice daily initially, adjusted according to response.

Intravenous Administration:

• Edema: 20-40 mg IV push over 1-2 minutes, may repeat in 2 hours with increased dose if inadequate response.
• Acute Pulmonary Edema: 40 mg IV over 1-2 minutes, repeated after 1 hour if necessary.

Dosing must be individualized based on renal function, with reduced doses or extended intervals in severe impairment. Monitor electrolyte levels and renal function regularly during therapy.

Precautions

• Monitor serum electrolytes, particularly potassium, sodium, and magnesium, at regular intervals
• Assess renal function before and during therapy, as deteriorating renal function may necessitate dose adjustment
• Use caution in patients with hepatic cirrhosis and ascites due to risk of precipitating hepatic encephalopathy
• May cause photosensitivity reactions; advise patients to use sun protection
• Ototoxicity risk increases with rapid IV administration, concurrent ototoxic drugs, or renal impairment
• Monitor for signs of volume depletion and orthostatic hypotension
• Use with caution in patients with sulfonamide allergy (cross-reactivity possible)
• May increase blood glucose levels; monitor diabetics closely

Contraindications

• Anuria unresponsive to furosemide trial dose
• Hepatic coma or severe electrolyte depletion
• Hypersensitivity to furosemide or sulfonamide-derived drugs
• Severe hypokalemia or hyponatremia
• Concomitant use with aminoglycosides in renal impairment (increased ototoxicity risk)

Possible side effect

Common (≥1%):

• Dehydration and volume depletion
• Hypokalemia (dose-dependent)
• Hyponatremia
• Hypochloremic alkalosis
• Orthostatic hypotension
• Hyperglycemia
• Hyperuricemia

Less Common (<1%):

• Ototoxicity (tinnitus, hearing loss)
• Pancreatitis
• Photosensitivity reactions
• Blood dyscrasias (thrombocytopenia, leukopenia)
• Skin rash and pruritus
• Dizziness and headache
• Gastrointestinal disturbances (nausea, constipation)

Drug interaction

• Digoxin: Hypokalemia may potentiate digitalis toxicity
• Lithium: Reduced renal clearance may cause lithium toxicity
• NSAIDs: May attenuate diuretic and antihypertensive effects
• Aminoglycosides: Increased risk of ototoxicity and nephrotoxicity
• Probenecid: Inhibits diuretic response
• Antihypertensive agents: Potentiates hypotensive effects
• Corticosteroids: Enhanced potassium wasting
• Sucralfate: Reduces furosemide absorption (separate administration by 2 hours)

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is nearly time for the next scheduled dose. Do not double the dose to make up for a missed administration. For twice-daily regimens, if remembered within 4 hours of the scheduled time, take the missed dose. Otherwise, skip and resume normal schedule. For once-daily dosing, take when remembered unless within 8 hours of next dose.

Overdose

Symptoms include profound water and electrolyte depletion (dehydration, hypovolemia, hypotension, hypokalemia, hyponatremia, hypochloremic alkalosis), which may progress to circulatory collapse and thrombosis. Treatment involves cessation of therapy and vigorous electrolyte and volume replacement. Hemodialysis does not significantly enhance elimination. Monitor fluid and electrolyte status closely for 48-72 hours post-overdose.

Storage

Store at controlled room temperature (20-25°C or 68-77°F). Protect from light and moisture. Keep in original container with tight closure. Do not freeze oral solution or intravenous preparation. Discard any unused portion of IV solution after single use. Keep out of reach of children.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional before starting or changing any medication regimen. The prescribing physician should be familiar with the complete prescribing information and should monitor patients appropriately during therapy. Individual response to medication may vary.

Reviews

“Furosemide remains the gold standard for rapid diuresis in acute decompensated heart failure. Its predictable response and flexible dosing make it indispensable in critical care settings.” - Cardiology Specialist

“While effective, requires careful monitoring of electrolytes, particularly in elderly patients with comorbid conditions. The risk of hypokalemia necessitates frequent assessment and often potassium supplementation.” - Nephrology Consultant

“Excellent efficacy in managing resistant hypertension when combined with other antihypertensive agents. The oral formulation allows for convenient long-term management in outpatient settings.” - Internal Medicine Physician