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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium, chloride, and potassium in the ascending limb of the loop of Henle, leading to increased excretion of water and electrolytes.
## Primary Indications
* Edema associated with congestive heart failure (CHF), liver cirrhosis, and renal disease (including the nephrotic syndrome).
* Hypertension (IV or oral formulation, usually in combination with other antihypertensives).
* Acute pulmonary edema.
## Adult Dosing
* **Edema:** Oral: 20-80 mg once daily. May be increased by 20-40 mg every 6-8 hours as needed. Doses may be given less frequently (e.g., every other day or every 2-3 days) in some patients. Maximum oral dose typically 600 mg/day, but higher doses have been used in refractory cases under close monitoring.
* **Edema (IV/IM):** 20-40 mg once daily. If no adequate response, may be increased by 20 mg every 2 hours. Maximum IV/IM dose typically 600 mg/day, but higher doses may be used in refractory cases.
* **Hypertension:** Oral: 40 mg twice daily. Not typically a first-line agent for hypertension monotherapy.
* **Acute Pulmonary Edema (IV):** 20-40 mg IV. May be repeated every 2 hours as needed.
*Note: Dosing for edematous states is highly individualized and may require specific protocols.*
## Pediatric Dosing
* **Edema:** Oral: 1-2 mg/kg/dose once daily. May be increased by 1 mg/kg/dose every 6-8 hours. Maximum dose: 6 mg/kg/day.
* **Edema (IV/IM):** 1 mg/kg/dose once daily. May be increased by 1 mg/kg/dose every 2 hours. Maximum dose: 6 mg/kg/day.
* **Premature infants:** May require lower doses due to immature renal function. Consult specialized pediatric literature.
## Dose Adjustments
* **Renal Impairment:** Dose reduction may be necessary, especially in patients with severe renal impairment. However, higher doses may be required to achieve diuresis in some cases of renal failure. Monitor response closely.
* **Hepatic Impairment:** Caution advised. Electrolyte and fluid balance can be significantly altered.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* Electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia).
* Dehydration, hypotension.
* Ototoxicity (hearing loss, tinnitus), particularly with rapid IV administration or high doses.
* Hyperuricemia, gout.
* Hyperglycemia.
* Dizziness, lightheadedness.
* Aplastic anemia, agranulocytosis, thrombocytopenia (rare).
* Photosensitivity.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **NSAIDs:** May reduce diuretic and antihypertensive effects, and increase risk of renal impairment.
* **Lithium:** May decrease lithium clearance, increasing risk of lithium toxicity.
* **Potassium-sparing diuretics, ACE inhibitors, ARBs, spironolactone:** Increased risk of hyperkalemia.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Risk of digoxin toxicity is increased in the presence of furosemide-induced hypokalemia.
* **Antihypertensives:** Additive hypotensive effect.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Renal function (BUN, creatinine).
* Fluid balance (intake and output, daily weights).
* Blood pressure.
* Auditory function (especially with high doses or rapid IV infusion).
* Blood glucose in diabetic patients.
## Clinical Pearls
* Administer oral furosemide in the morning to minimize nocturia.
* Rapid IV administration can increase the risk of ototoxicity. Infuse slowly (e.g., over 30-60 minutes) or as an intermittent infusion.
* Monitor for signs of electrolyte depletion (muscle cramps, weakness, arrhythmias).
* Consider potassium supplementation or a potassium-sparing diuretic if hypokalemia occurs and is symptomatic or if the patient is on digoxin.
* Furosemide can be effective in patients with renal failure, but requires careful titration and monitoring.
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*Disclaimer: This information is intended for educational purposes and does not substitute for professional medical advice. Always consult the most current prescribing information and your healthcare provider for any questions regarding drug therapy.*
