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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. This leads to increased excretion of these electrolytes and water.
## Primary Indications
* Edema associated with congestive heart failure (CHF)
* Edema associated with hepatic cirrhosis
* Edema associated with renal disease, including the nephrotic syndrome
* Hypertension (adjunctive therapy)
## Adult Dosing
* **Edema:**
* Oral: Start with 20-80 mg once daily. If needed, dose can be increased by 20-40 mg every 6-8 hours until desired response is obtained. Maximum oral dose is typically 600 mg/day, but higher doses have been used under close medical supervision.
* Intravenous (IV)/Intramuscular (IM): Start with 20-40 mg once daily. If needed, dose can be increased by 20 mg every 2 hours until desired response is obtained. Maximum IV/IM dose is typically 600 mg/day, but higher doses may be necessary in severe cases and require close monitoring.
* **Hypertension:**
* Oral: 40 mg twice daily. May be used in combination with other antihypertensives.
Dosing for edema can be highly individualized and may require specific protocols for initiation and titration.
## Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose given once or twice daily. Maximum dose is 6 mg/kg/day.
* IV/IM: 1 mg/kg/dose. Maximum dose is 6 mg/kg/day.
## Dose Adjustments
* **Renal Impairment:** In patients with severe renal impairment, initial doses may need to be reduced. However, higher doses may be required to achieve a diuretic effect due to resistance. Careful titration and monitoring are essential.
* **Hepatic Impairment:** Patients with hepatic cirrhosis may be more sensitive to the effects of furosemide, particularly regarding electrolyte and fluid balance. Dosing should be initiated at lower levels and titrated cautiously.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides (potential for cross-sensitivity)
## Adverse Effects
* **Electrolyte disturbances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and hypotension.**
* **Ototoxicity:** Hearing impairment, tinnitus (more common with rapid IV administration or high doses).
* **Hyperglycemia.**
* **Hyperuricemia:** May precipitate gout.
* **Photosensitivity.**
* **Aplastic anemia, thrombocytopenia, agranulocytosis** (rare).
* **Acute kidney injury.**
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **ACE inhibitors/ARBs:** Increased risk of hypotension and azotemia.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, increasing lithium levels and risk of toxicity.
* **NSAIDs:** May reduce diuretic and antihypertensive effects and increase risk of kidney damage.
* **Potassium supplements/Potassium-sparing diuretics:** Monitor potassium levels closely.
## Monitoring
* **Electrolytes:** Sodium, potassium, chloride, magnesium, calcium, bicarbonate.
* **Renal function:** Serum creatinine, BUN.
* **Fluid balance:** Intake and output, daily weights.
* **Blood pressure:** Especially with IV administration.
* **Hearing:** Assess for tinnitus or hearing loss.
## Clinical Pearls
* Administer oral furosemide with food or milk to minimize gastric irritation.
* For IV administration, infuse slowly to reduce the risk of ototoxicity. Avoid rapid IV push.
* Monitor for signs of dehydration and electrolyte imbalance, especially in elderly patients or those with significant fluid losses.
* Consider potassium supplementation or concurrent use of a potassium-sparing diuretic if hypokalemia is persistent or symptomatic.
* Furosemide can be less effective in patients with significant renal impairment; higher doses or alternative diuretics may be needed.
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*Disclaimer: This information is intended for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional and refer to the most current prescribing information and relevant guidelines for specific patient care decisions.*
