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## Furosemide (Lasix)
### Overview
Furosemide is a potent loop diuretic used to reduce fluid overload and manage edema associated with various conditions.
### Primary Indications
* Edema due to heart failure, liver cirrhosis, or renal disease (including nephrotic syndrome).
* Hypertension (less commonly, typically in conjunction with other agents for resistant hypertension).
* Acute pulmonary edema.
### Adult Dosing
* **Edema:**
* Oral: Start with 20-80 mg once daily. May increase by 20-40 mg every 6-8 hours as needed. Usual maintenance dose is 40-120 mg once daily or divided doses.
* Intravenous (IV)/Intramuscular (IM): Start with 20-40 mg once daily. If inadequate response, dose can be increased by 20 mg every 2 hours.
* Continuous IV infusion: Typically initiated at 4 mg/minute after a bolus dose.
* Maximum daily dose generally not to exceed 600 mg, although higher doses may be used in select cases under close monitoring.
* **Hypertension:**
* Oral: 40 mg twice daily.
* **Acute Pulmonary Edema:**
* IV: 20-40 mg. If response is inadequate, may repeat dose in 30-60 minutes. May escalate to continuous infusion.
### Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose every 6-12 hours.
* IV/IM: 1 mg/kg/dose every 6-12 hours.
* Maximum dose: 6 mg/kg/day (oral) or 2 mg/kg/dose (IV/IM).
* **Neonatal Use:** Due to immature renal function, lower doses may be necessary, and careful monitoring is essential. Dosing varies significantly based on clinical context and gestational age; consult specific neonatal guidelines.
### Dose Adjustments
* **Renal Impairment:** Higher doses may be required due to reduced renal excretion. Monitor electrolytes and renal function closely.
* **Hepatic Impairment:** Dose may need to be reduced, especially in patients with ascites, due to altered pharmacokinetics and risk of hepatic encephalopathy.
### Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides (caution advised).
* Severe electrolyte depletion (e.g., hypokalemia, hyponatremia).
### Adverse Effects
* **Common:** Dizziness, lightheadedness, dehydration, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), hypotension, hyperuricemia (may precipitate gout).
* **Less Common:** Ototoxicity (especially with rapid IV administration or high doses), rash, photosensitivity, hyperglycemia.
### Key Drug Interactions
* **Aminoglycosides, Cisplatin:** Increased risk of ototoxicity.
* **ACE Inhibitors, ARBs, Other Antihypertensives:** Additive hypotensive effect.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, increasing risk of lithium toxicity.
* **NSAIDs:** May reduce the diuretic and antihypertensive effects of furosemide.
* **Potassium-Sparing Diuretics (e.g., Spironolactone, Amiloride):** Counteract potassium loss but can lead to hyperkalemia.
* **Theophylline:** May increase the risk of theophylline toxicity.
### Monitoring
* **Electrolytes:** Sodium, potassium, chloride, magnesium, calcium (especially during initiation and dose changes).
* **Renal Function:** BUN, creatinine.
* **Fluid Balance:** Intake and output, daily weights.
* **Blood Pressure:** Especially with IV administration or in hypertensive patients.
* **Auditory Function:** Report tinnitus or hearing loss.
### Clinical Pearls
* Furosemide is a potent diuretic; rapid diuresis can lead to dehydration and electrolyte disturbances.
* Administer IV furosemide slowly (over at least 1-2 minutes) to reduce the risk of ototoxicity. Continuous infusion may be preferred in some patients to avoid rapid fluctuations.
* For patients with ascites, oral furosemide may be less effective than IV due to altered absorption.
* Monitor for signs of hypokalemia (muscle cramps, weakness, arrhythmias). Consider potassium supplementation or a potassium-sparing diuretic if hypokalemia is significant.
* Diuresis can be enhanced when furosemide is administered with other diuretics (e.g., thiazides), but this increases the risk of electrolyte abnormalities.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant literature for complete details before making clinical decisions.
