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## Furosemide (Lasix)
### Overview
Furosemide is a potent loop diuretic used to treat edema associated with congestive heart failure, liver cirrhosis, and renal disease, including the nephrotic syndrome. It is also used to treat hypertension, usually in combination with other antihypertensive agents.
### Primary Indications
* Edema (congestive heart failure, hepatic cirrhosis, renal disease)
* Hypertension
### Adult Dosing
* **Edema:**
* **Initial:** 20-80 mg orally once daily. May be given in divided doses.
* **Maximum:** 600 mg orally daily (higher doses may be used in specific cases under close medical supervision).
* **Intermittent IV/IM:** 20-40 mg intravenously or intramuscularly once.
* **Continuous IV Infusion:** 4 mg/hour after an initial IV bolus of 40 mg.
* **Hypertension:**
* **Initial:** 40 mg orally twice daily.
* **Maintenance:** Adjust dose based on response. Usually combined with other antihypertensives.
### Pediatric Dosing
* **Edema:**
* **Oral:** 1-2 mg/kg/dose once daily, not to exceed 6 mg/kg/day.
* **IV/IM:** 1 mg/kg/dose once daily, not to exceed 6 mg/kg/day.
### Dose Adjustments
* **Renal Impairment:** Patients with severe renal impairment may require higher doses due to decreased GFR and impaired tubular secretion. Dose and frequency should be adjusted based on response and degree of renal impairment.
* **Hepatic Impairment:** Use with caution; edema may be related to ascites. Monitor electrolytes and fluid status closely.
### Contraindications
* Anuria.
* Known hypersensitivity to furosemide or its sulfonamide constituents.
* Use with extreme caution in patients with severe electrolyte depletion (e.g., hypokalemia, hyponatremia) or volume depletion.
### Adverse Effects
Common: Dizziness, lightheadedness, headache, muscle cramps, weakness, orthostatic hypotension.
Serious: Severe electrolyte abnormalities (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), dehydration, ototoxicity (especially with rapid IV administration or high doses, or in renal impairment), hyperuricemia, hyperglycemia, pancreatitis, aplastic anemia, agranulocytosis, thrombocytopenia, rash.
### Key Drug Interactions
* **Aminoglycosides/Other Ototoxic Drugs:** Increased risk of ototoxicity.
* **Corticosteroids/ACTH:** Increased risk of electrolyte imbalance, particularly hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May reduce the diuretic and antihypertensive effects of furosemide.
* **Potassium-Sparing Diuretics (e.g., spironolactone, amiloride) or Potassium Supplements:** May antagonize the diuretic effect or increase the risk of hyperkalemia.
* **ACE Inhibitors/ARBs:** Additive hypotensive effect; increased risk of severe hypotension and renal dysfunction, particularly in volume-depleted patients.
* **Lithium:** Reduced renal clearance of lithium, leading to increased serum lithium levels and risk of toxicity.
### Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Fluid balance (intake and output)
* Weight
* Blood pressure
* Renal function (BUN, creatinine)
* Hearing (especially with high doses or prolonged therapy)
* Blood glucose and uric acid levels
### Clinical Pearls
* Oral administration may be preferred for chronic management of edema due to more sustained effect.
* IV administration is generally more rapid and potent than oral.
* Rapid IV administration can increase the risk of ototoxicity. Administer IV infusion slowly (over 30-60 minutes).
* Electrolyte replacement may be necessary, particularly potassium.
* Monitor for signs of dehydration and hypotension, especially in elderly patients or those on concomitant antihypertensive therapy.
* For patients with refractory edema, continuous IV infusion may be more effective than intermittent dosing.
**Disclaimer:** This information is intended for clinical use and does not replace the official prescribing information or professional medical advice. Always consult the current drug monograph and patient-specific factors before initiating or modifying therapy.
