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## Furosemide (Lasix)
### Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, liver disease, and renal disease, including nephrotic syndrome. It is also used to treat hypertension, usually in combination with other antihypertensives.
### Primary Indications
* Edema due to heart failure, liver cirrhosis, and renal disease
* Hypertension
### Adult Dosing
* **Edema:**
* **Oral:** The usual starting dose is 20 mg to 80 mg once daily. Doses can be increased by 20 mg to 40 mg every 6 to 8 hours as needed. The maximum daily dose is typically 600 mg, but higher doses may be used cautiously under specialist supervision.
* **Intravenous (IV) or Intramuscular (IM):** The usual starting dose is 20 mg to 40 mg once daily. Doses can be increased by 20 mg every 2 hours as needed. The maximum daily dose is typically 600 mg, but higher doses may be used cautiously under specialist supervision.
* **Continuous IV infusion:** Usually initiated at 4 mg/minute after an initial bolus dose.
* **Hypertension:**
* **Oral:** The usual starting dose is 40 mg twice daily. This may be adjusted based on response. Furosemide is typically not the first-line agent for hypertension and is often used in patients with coexisting edema.
### Pediatric Dosing
* **Edema:**
* **Oral:** 1 mg/kg to 2 mg/kg per dose once daily, not to exceed 6 mg/kg/day. Doses may be given every 6 hours if needed.
* **IV or IM:** 1 mg/kg per dose once daily, not to exceed 6 mg/kg/day. Doses may be given every 6 hours if needed.
### Dose Adjustments
* **Renal Impairment:** Dose adjustments may be necessary. In patients with severe renal impairment, accumulation can occur. Dosing should be guided by response and renal function.
* **Hepatic Impairment:** Furosemide can accumulate in patients with hepatic impairment. Dosing should be cautious and guided by response.
### Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides
### Adverse Effects
Common adverse effects include dizziness, lightheadedness, electrolyte imbalance (hypokalemia, hyponatremia, hypochloremia), dehydration, hypotension, and increased urination. Less common but serious effects include ototoxicity (especially with rapid IV administration or high doses), hyperglycemia, and hyperuricemia.
### Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity.
* **NSAIDs:** May reduce the diuretic and antihypertensive effect of furosemide; may increase the risk of nephrotoxicity.
* **Lithium:** Furosemide can decrease lithium clearance, increasing the risk of lithium toxicity.
* **Antihypertensives:** Additive hypotensive effects.
* **Digoxin:** Electrolyte disturbances induced by furosemide (e.g., hypokalemia) can increase digoxin toxicity.
* **Corticosteroids:** Increased risk of hypokalemia.
### Monitoring
* Electrolytes (sodium, potassium, chloride)
* Renal function (BUN, creatinine)
* Blood pressure
* Urine output
* Auditory function (especially with high doses or prolonged therapy)
### Clinical Pearls
* Administer oral furosemide with food or milk to minimize gastrointestinal upset.
* Rapid IV administration can increase the risk of ototoxicity. Administer IV doses slowly (e.g., over 30-60 minutes) or via continuous infusion.
* Patients on furosemide therapy are at increased risk for hypokalemia, which can lead to arrhythmias, especially in those taking digoxin. Potassium supplementation or potassium-sparing diuretics may be necessary.
* Monitor for signs of dehydration and electrolyte imbalance, especially in elderly patients or those with significant fluid losses.
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*This information is intended for healthcare professionals. Always verify the most current prescribing information with an official drug compendium or the manufacturer's product information before making clinical decisions.*
