Lasix (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 is also used alone or in combination with other antihypertensive agents in the treatment of hypertension. This medication acts on the ascending limb of the loop of Henle to inhibit the reabsorption of sodium and chloride, promoting significant diuresis and subsequent reduction in extracellular fluid volume. Its rapid onset and potent efficacy make it a cornerstone in acute and chronic fluid overload management.

Features

• Active ingredient: Furosemide
• Available in oral tablets (20 mg, 40 mg, 80 mg) and injectable formulations
• Onset of action: Oral within 60 minutes; IV within 5 minutes
• Peak effect: 1–2 hours (oral); 30 minutes (IV)
• Duration: 6–8 hours
• Excretion: Primarily renal, with some hepatic metabolism
• Pregnancy category: C (risk not ruled out)

Benefits

• Rapid and significant reduction of edema in congestive heart failure, hepatic cirrhosis, and renal impairment
• Effective lowering of blood pressure through reduction in plasma and extracellular fluid volume
• Useful in treating hypercalcemia due to enhanced calcium excretion
• Management of acute pulmonary edema through prompt diuresis
• Facilitates fluid balance in critically ill patients
• May reduce cardiac preload and afterload in acute decompensated heart failure

Common use

Lasix is commonly prescribed for conditions characterized by fluid retention. In congestive heart failure, it alleviates symptoms like dyspnea and peripheral edema by reducing preload. For patients with hepatic cirrhosis, it addresses ascites and edema when sodium restriction alone is insufficient. In renal disorders such as nephrotic syndrome, it mitigates edema by counteracting sodium retention. Off-label uses include hypercalcemia and hypertension resistant to thiazide diuretics. It is also employed in acute settings, such as hypertensive crises and acute renal failure, to induce forced diuresis.

Dosage and direction

Dosage must be individualized based on patient response and clinical condition. For edema in adults, the usual initial oral dose is 20 to 80 mg given as a single dose. Depending on the patient’s response, another dose may be administered 6 to 8 hours later. This may be 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 has been obtained. The maintenance dose may be given once or twice daily. For hypertension, the typical starting dose is 40 mg twice daily, adjusted based on blood pressure response. In pediatric patients, the initial oral dose is 2 mg/kg body weight, given as a single dose; if 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. Injectable forms are reserved for urgent situations or when oral administration is not feasible; IV doses should be administered slowly over 1 to 2 minutes.

Precautions

Patients should be monitored for signs of fluid and electrolyte imbalance, particularly hypokalemia, hyponatremia, and hypochloremic alkalosis. Serum electrolytes, BUN, and creatinine should be checked periodically, especially during initial therapy or after dose adjustments. Use with caution in patients with hepatic cirrhosis and ascites, as sudden electrolyte imbalance may precipitate hepatic encephalopathy. Ototoxicity, which may be irreversible, has been reported; risk is increased with rapid IV injection, high doses, and concurrent use of other ototoxic drugs. Lasix may increase blood glucose and uric acid levels; diabetic and gouty patients should be monitored closely. Orthostatic hypotension may occur, especially in volume-depleted patients.

Contraindications

Lasix is contraindicated in patients with anuria or hypersensitivity to furosemide or sulfonamide-derived drugs. It is also contraindicated in hepatic coma and in states of severe electrolyte depletion until the condition is improved or corrected. Avoid use in patients with a history of sulfonamide allergy due to potential cross-reactivity.

Possible side effect

Common adverse reactions include dizziness, headache, blurred vision, orthostatic hypotension, and gastrointestinal disturbances such as nausea, vomiting, or diarrhea. Electrolyte imbalances like hypokalemia, hyponatremia, hypocalcemia, and hypomagnesemia may occur. Ototoxicity, manifesting as tinnitus, hearing loss, or deafness (often reversible but sometimes permanent), has been reported, particularly with rapid IV administration or high doses. Other potential side effects include hyperglycemia, hyperuricemia, rash, photosensitivity, and blood dyscrasias such as leukopenia or thrombocytopenia. Rarely, pancreatitis and interstitial nephritis may occur.

Drug interaction

Lasix may potentiate the effects of other antihypertensive agents, leading to pronounced hypotension. Concomitant use with aminoglycosides, cisplatin, or other ototoxic drugs increases the risk of ototoxicity. It may reduce renal clearance of lithium, increasing the risk of lithium toxicity. NSAIDs may attenuate the diuretic and antihypertensive effects of Lasix. Probenecid may inhibit the secretion of furosemide, reducing its efficacy. Corticosteroids and amphotericin B may exacerbate hypokalemia. Lasix may enhance the effects of neuromuscular blocking agents. Use with digoxin requires careful monitoring due to increased risk of digoxin toxicity secondary to hypokalemia.

Missed dose

If a dose is missed, it should be taken as soon as remembered, unless it is almost time for the next scheduled dose. In that case, the missed dose should be skipped, and the regular dosing schedule resumed. Doubling the dose to make up for a missed one is not recommended, as it may increase the risk of adverse effects such as dehydration or electrolyte imbalance.

Overdose

Overdose may lead to profound diuresis with water and electrolyte depletion, manifested by dehydration, hypovolemia, hypotension, tachycardia, and circulatory collapse. Electrolyte imbalances such as hypokalemia, hyponatremia, and hypochloremia may occur. Treatment is supportive and includes cessation of Lasix, replacement of fluid and electrolytes, and monitoring of vital signs and renal function. Hemodialysis does not accelerate elimination of furosemide.

Storage

Store at room temperature (15–30°C or 59–86°F) in a tightly closed container, protected from light and moisture. Keep out of reach of children. Do not use if the product appears discolored or contains particulate matter. For injectable forms, follow specific storage instructions provided by the manufacturer, and do not use if cloudy or precipitated.

Disclaimer

This information is for educational purposes only and 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 medication. Do not disregard professional medical advice or delay in seeking it because of something you have read here. Dosage and indications may vary based on individual patient factors and should be determined by a healthcare professional.

Reviews

Clinical studies and meta-analyses consistently demonstrate the efficacy of furosemide in reducing edema and improving symptoms in heart failure and renal impairment. For instance, a 2019 systematic review in the Journal of Cardiac Failure confirmed its role as first-line therapy for acute decompensated heart failure, though highlighting the need for careful electrolyte monitoring. Patient reviews often note significant symptom relief but occasionally report side effects like muscle cramps or dizziness, emphasizing the importance of individualized dosing and monitoring. Overall, it remains a widely trusted and effective agent in clinical practice.