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## Furosemide (Lasix)
### Overview
Furosemide is a potent loop diuretic used for the management of edema associated with heart failure, liver cirrhosis, and renal disease, including the nephrotic syndrome. It is also used to manage hypertension, although it is not a first-line agent.
### Primary Indications
* Edema secondary to heart failure, liver cirrhosis, and renal disease.
* Hypertension (adjunctive therapy).
### Adult Dosing
* **Edema:**
* Oral: The usual starting dose is 20-80 mg once or twice daily. Doses can be increased by 20-40 mg every 6-8 hours as needed. The maintenance dose varies widely.
* Intravenous (IV): The usual starting dose is 20-40 mg IV once. Doses can be increased by 20 mg every 2 hours as needed.
* Maximum oral dose: Not well-defined, but doses up to 600 mg daily have been used in severe cases under close medical supervision.
* Maximum IV dose: Doses up to 200 mg in a single dose have been used, but higher doses may be required for patients with significant renal impairment. Continuous infusions are also an option.
* **Hypertension:**
* Oral: 40 mg twice daily.
### Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose once or twice daily. Maximum dose is 6 mg/kg/day.
* IV: 1 mg/kg/dose once. Maximum dose is 6 mg/kg/day.
### Dose Adjustments
* **Renal Impairment:** Patients with renal impairment may require higher doses due to impaired drug absorption and excretion. Dosing should be individualized.
* **Hepatic Impairment:** Caution is advised due to risk of electrolyte imbalances and hepatic encephalopathy.
### Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
### Adverse Effects
* **Electrolyte imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and hypotension.**
* **Ototoxicity:** Especially with rapid IV administration or high doses.
* **Hyperglycemia.**
* **Hyperuricemia.**
* **Photosensitivity.**
* **Dermatologic reactions:** Rash, Stevens-Johnson syndrome (rare).
### Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **Antihypertensives:** Additive hypotensive effects.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May reduce diuretic and antihypertensive effects.
* **Lithium:** Reduced renal clearance of lithium, increasing lithium toxicity risk.
* **Potassium-sparing diuretics:** May be used to counteract potassium loss, but requires careful monitoring.
### Monitoring
* **Electrolytes:** Serum electrolytes (sodium, potassium, chloride, magnesium, calcium) should be monitored regularly, especially during initiation and dose changes.
* **Renal function:** Serum creatinine and BUN.
* **Fluid status:** Daily weights, intake and output.
* **Blood pressure.**
* **Blood glucose and uric acid levels** in susceptible individuals.
### Clinical Pearls
* Furosemide can cause significant volume and electrolyte depletion; monitor closely.
* For patients with edema, assess for underlying cause and response to therapy.
* Rapid IV administration can increase the risk of ototoxicity. Administer slowly over 30-60 minutes or as a continuous infusion.
* To minimize nocturia, administer the last dose of the day no later than 4-6 hours before bedtime.
* Oral and IV doses are not always interchangeable on a milligram-per-milligram basis, especially in patients with edema. Often, a higher IV dose is required compared to the oral dose.
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*This information is intended for healthcare professionals and should not be a substitute for professional medical advice. Always consult the most current prescribing information and guidelines.*
