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# Lasix (Furosemide)
## Overview
Furosemide is a potent loop diuretic that inhibits the Na+-K+-2Cl- symporter in the thick ascending limb of the loop of Henle, promoting the excretion of sodium, chloride, and water.
## Primary Indications
* Edema associated with congestive heart failure (CHF), hepatic cirrhosis, and renal impairment (including nephrotic syndrome).
* Hypertension (adjunct therapy).
## Adult Dosing
* **Edema:** Initial oral dose is 20–80 mg once daily. If response is inadequate, increase in increments of 20–40 mg no sooner than 6–8 hours after the previous dose until desired effect is achieved. Max dose is typically 600 mg/day (rarely needed).
* **Hypertension:** 20–40 mg twice daily.
## Pediatric Dosing
* **Edema:** Initial oral dose is 2 mg/kg/dose once or twice daily. May increase by 1–2 mg/kg/dose every 6–8 hours as needed.
* **Maximum:** 6 mg/kg/dose; do not exceed 600 mg/day. Dosing is highly dependent on institutional protocols; verify unit-specific guidelines for neonatal vs. pediatric indications.
## Dose Adjustments
* **Renal Impairment:** No specific adjustment required for mild-to-moderate impairment, but higher doses may be required in severe renal failure.
* **Hepatic Impairment:** Reduce initial doses to avoid rapid electrolyte imbalances or precipitation of hepatic encephalopathy.
## Contraindications
* Anuria.
* Hypersensitivity to furosemide or sulfonamides.
* Severe electrolyte depletion (hypokalemia, hyponatremia, hypovolemia).
* Hepatic coma or states of severe electrolyte depletion.
## Adverse Effects
* **Common:** Dry mouth, polyuria, orthostatic hypotension.
* **Severe:** Hypokalemia, hyponatremia, hypomagnesemia, hyperuricemia, ototoxicity (dose-related), and dehydration.
## Key Drug Interactions
* **Aminoglycosides:** Risk of additive ototoxicity and nephrotoxicity.
* **Lithium:** Furosemide may decrease lithium renal clearance, increasing risk of toxicity.
* **NSAIDs:** May reduce the natriuretic and antihypertensive effects of furosemide; risk of acute renal failure in volume-depleted patients.
* **Digoxin:** Increased risk of digoxin-related arrhythmia due to hypokalemia.
## Monitoring
* **Essential:** Serum electrolytes (potassium, sodium, magnesium), BUN/Creatinine, blood pressure, and daily weights.
* **Signs of Toxicity:** Monitor for tinnitus (ototoxicity), dizziness, or signs of volume depletion (tachycardia, hypotension).
## Clinical Pearls
* **Diuretic Resistance:** If oral bioavailability is poor due to bowel edema, transition to IV administration (usually at 50% of the oral dose).
* **Timing:** Administer early in the day (e.g., 08:00 and 14:00) to avoid nocturia.
* **Safety:** Monitor elderly patients closely for falls secondary to orthostasis and sudden urgency.
* **Uncertainty Note:** Dosing for refractory heart failure or advanced renal disease often exceeds standard labels; strictly follow institutional clinical titration protocols.
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**Disclaimer:** This information is intended for educational purposes only. Always verify current prescribing information, institutional protocols, and patient-specific factors via reliable clinical databases (e.g., Lexicomp, UpToDate) before administering medication.
