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## Furosemide (Lasix)
### Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) due to conditions such as heart failure, liver disease, and kidney disease. It also treats high blood pressure, often in combination with other medications.
### Primary Indications
* Edema associated with congestive heart failure, liver cirrhosis, and renal disease (including nephrotic syndrome).
* Hypertension.
### Adult Dosing
* **Edema:**
* Oral: Typically initiated at 20-80 mg once or twice daily. The dose can be increased by 20-40 mg every 6-8 hours as needed.
* Intravenous (IV) or Intramuscular (IM): Typically initiated at 20-40 mg once. If insufficient response, doses may be repeated every 2 hours, or increased by 20 mg per dose. Continuous IV infusion may be considered.
* Maximum daily oral dose: Generally 600 mg, though higher doses have been used under close supervision in specific circumstances.
* Maximum IV/IM dose: No strict maximum, depends on clinical response and patient tolerance.
* **Hypertension:**
* Oral: Typically initiated at 40 mg twice daily. Doses may be adjusted based on response.
* Furosemide is usually not a first-line agent for hypertension unless edema is also present.
### Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose once or twice daily. Maximum: 6 mg/kg/dose per day.
* IV or IM: 1 mg/kg/dose once. If insufficient response, doses may be repeated every 2 hours, or increased by 1 mg/kg per dose. Maximum: 6 mg/kg/dose per day.
* **Neonatal doses:** Specific protocols may vary; consult neonatology guidelines.
### Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in patients with renal impairment due to reduced protein binding and altered tubular secretion. However, caution is advised as impaired renal function can lead to accumulation.
* **Hepatic Impairment:** Use with caution; ascites may affect drug distribution. Monitor for electrolyte and fluid balance changes.
### Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
### Adverse Effects
Common adverse effects include dizziness, lightheadedness, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia), dehydration, hyperuricemia, hyperglycemia, and hypotension. Less common but serious effects include ototoxicity (especially with rapid IV administration or high doses), Stevens-Johnson syndrome, and aplastic anemia.
### Key Drug Interactions
* **Aminoglycosides, other ototoxic drugs:** Increased risk of ototoxicity.
* **Corticosteroids:** Increased risk of hypokalemia.
* **NSAIDs:** May reduce diuretic and antihypertensive effects, and increase risk of renal impairment.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Antihypertensives:** Additive hypotensive effects.
* **Lithium:** Increased risk of lithium toxicity due to decreased renal clearance.
### Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Fluid balance (intake and output, daily weights).
* Renal function (BUN, creatinine).
* Blood pressure.
* Blood glucose in diabetic patients.
* Uric acid levels.
* Hearing assessment, especially with high doses or IV administration.
### Clinical Pearls
* Administer IV furosemide slowly to minimize the risk of ototoxicity. Rapid IV injection is associated with a higher incidence of hearing impairment.
* Oral and IV doses are not always interchangeable on a mg-to-mg basis. A general conversion is approximately 1 mg IV = 2 mg oral, but this can vary significantly.
* Patients with severe edema may require higher doses or continuous infusions for adequate diuresis.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before administering any medication.
