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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium and chloride in the ascending limb of the loop of Henle, leading to increased excretion of water, sodium, chloride, potassium, calcium, magnesium, and hydrogen.
## Primary Indications
* Edema associated with congestive heart failure (CHF), liver cirrhosis, and renal disease (including the nephrotic syndrome).
* Hypertension (usually used in combination with other antihypertensives).
## Adult Dosing
* **Edema:** 20-80 mg orally once daily. May increase by 20-40 mg every 6-8 hours as needed. Usual maintenance dose: 20-40 mg orally once or twice daily. Doses as high as 600 mg/day have been used in severe cases.
* **Hypertension:** 40 mg orally twice daily.
## Pediatric Dosing
* **Edema:** 1-2 mg/kg orally once daily. May increase by 1 mg/kg every 6-8 hours as needed. Maximum dose: 6 mg/kg/day.
* **Neonatal hyperbilirubinemia (off-label, limited evidence):** Doses vary widely and are not well-established.
## Dose Adjustments
* **Renal Impairment:** Doses may need to be increased in patients with severe renal impairment due to decreased drug bioavailability and increased protein binding. However, caution is advised as high doses can be nephrotoxic.
* **Hepatic Impairment:** Use with caution; may precipitate hepatic coma.
## Contraindications
* Anuria.
* History of hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Electrolyte Imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and Hypotension:** Particularly with aggressive diuresis.
* **Ototoxicity:** Auditory impairment, tinnitus, deafness (more common with rapid IV administration or high doses).
* **Hyperuricemia:** May precipitate gout.
* **Hyperglycemia:** May occur, particularly in patients with diabetes.
* **Photosensitivity.**
* **Aplastic anemia, agranulocytosis, thrombocytopenia.**
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **NSAIDs:** May reduce the diuretic and antihypertensive effects of furosemide and increase the risk of nephrotoxicity.
* **ACE Inhibitors/ARBs:** Increased risk of hypotension and azotemia, especially in volume-depleted patients.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, leading to increased lithium levels and toxicity.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Serum electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Blood pressure
* Urine output
* Hearing (especially with high doses or IV administration)
## Clinical Pearls
* Administer oral furosemide in the morning to minimize nocturia.
* IV administration should be slow (e.g., over 20-30 minutes) to reduce the risk of ototoxicity.
* Potassium supplementation or a potassium-sparing diuretic may be necessary to prevent or manage hypokalemia, depending on the degree of diuresis and patient factors.
* Monitor for signs of dehydration (e.g., dry mouth, dizziness, decreased urine output).
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines for complete details and to verify dosages and safety information before prescribing.*
