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# Furosemide
## Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, liver cirrhosis, and renal disease, including the nephrotic syndrome. It is also used to treat hypertension, alone or in combination with other antihypertensives.
## Primary Indications
* Edema secondary to heart failure
* Edema secondary to liver disease (cirrhosis)
* Edema secondary to renal disease (including nephrotic syndrome)
* Hypertension
## Adult Dosing
* **Edema:**
* Oral: Start with 20-80 mg once daily. Doses may be increased by 20-40 mg every 6-8 hours as needed. The usual maintenance dose is 20-80 mg per day. Doses up to 600 mg per day have been used in severe cases, but higher doses increase the risk of adverse effects.
* Intravenous (IV) or Intramuscular (IM): Start with 20-40 mg once daily. If insufficient response, may increase dose by 20 mg every 2 hours. May be given as a continuous infusion.
* **Hypertension:**
* Oral: Start with 40 mg twice daily. May be adjusted to 40 mg once daily or 20 mg twice daily. Do not use as sole therapy for hypertension.
## Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose once or twice daily. Maximum dose: 6 mg/kg/day.
* IV or IM: 1 mg/kg/dose. Maximum dose: 20 mg/dose for infants and children up to 16 years. May increase by 1 mg/kg/dose every 2 hours.
* **Note:** Dosing may vary based on specific condition and local protocols.
## Dose Adjustments
* **Renal Impairment:** Dosing needs careful titration. Higher doses may be required, but monitor closely for electrolyte imbalances and ototoxicity.
* **Hepatic Impairment:** Use with caution. Monitor for electrolyte disturbances and hepatic encephalopathy.
## Contraindications
* Anuria
* Known hypersensitivity to furosemide or sulfonamides (cross-sensitivity may occur)
* Severe electrolyte depletion (e.g., hypokalemia, hyponatremia)
## Adverse Effects
Common: Dizziness, lightheadedness, electrolyte imbalance (hypokalemia, hyponatremia, hypochloremia), dehydration, hypotension, hyperuricemia, hyperglycemia.
Less Common: Ototoxicity (especially with rapid IV administration or high doses), rash, photosensitivity, gastrointestinal upset, increased creatinine.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **ACE Inhibitors/ARBs:** Increased risk of hypotension and renal dysfunction.
* **NSAIDs:** May reduce the diuretic and antihypertensive effects.
* **Lithium:** Furosemide can decrease lithium clearance, increasing lithium toxicity risk.
* **Potassium-Sparing Diuretics (e.g., spironolactone):** May be used to counteract potassium loss, but requires close monitoring.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride)
* Renal function (BUN, creatinine)
* Blood pressure
* Fluid balance (intake and output)
* Hearing (especially with high doses or IV administration)
* Blood glucose (in diabetic patients)
* Uric acid
## Clinical Pearls
* Administer oral furosemide with food or milk to minimize gastrointestinal upset.
* Rapid IV administration can cause ototoxicity. Infuse IV furosemide slowly (e.g., 20 mg over 1-
