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# Furosemide
## Overview
Furosemide is a loop diuretic used to treat edema associated with congestive heart failure, liver cirrhosis, and renal disease, including in nephrotic syndrome. It is also used to treat hypertension, although it is not a first-line agent.
## Primary Indications
* Edema (congestive heart failure, liver cirrhosis, renal disease)
* Hypertension
## Adult Dosing
* **Edema:** Oral: 20 mg to 80 mg once daily. If the patient does not respond adequately, the dose may be increased by 20 mg to 40 mg every 6 to 8 hours or the dose may be increased by 20 mg to 40 mg every day. The maximum daily dose is typically 600 mg, but higher doses have been used under specialist supervision. Intravenous: 20 mg to 40 mg once daily. If the patient does not respond adequately, the dose may be increased by 20 mg to 40 mg every 2 hours. The maximum daily dose is typically 200 mg in 24 hours, but higher doses have been used under specialist supervision.
* **Hypertension:** Oral: 40 mg twice daily. This indication is less common, and other antihypertensives are generally preferred.
## Pediatric Dosing
* **Edema:** Oral: 1 mg/kg/dose to 2 mg/kg/dose once daily, not to exceed 6 mg/kg/day. Intravenous: 1 mg/kg/dose, not to exceed 20 mg per dose. If inadequate response, doses may be repeated every 6 hours. Higher doses may be required in some cases.
## Dose Adjustments
* **Renal Impairment:** Dose adjustments are often necessary. Monitor closely for efficacy and adverse effects.
* **Hepatic Impairment:** Dose adjustments may be necessary due to altered metabolism and increased risk of electrolyte imbalances and hepatic encephalopathy.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides (caution due to cross-reactivity)
## Adverse Effects
Common: Dizziness, lightheadedness, headache, muscle cramps, weakness, orthostatic hypotension, and dehydration.
Serious: Electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), ototoxicity (especially with rapid IV administration or high doses), hyperglycemia, hyperuricemia (gout), increased BUN/creatinine, pancreatitis, rash, aplastic anemia, and Stevens-Johnson syndrome.
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **Antihypertensives:** Additive hypotensive effect.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, increasing lithium toxicity risk.
* **NSAIDs:** May decrease furosemide's diuretic and antihypertensive effect.
* **Potassium supplements and potassium-sparing diuretics:** Counteract potential hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Blood pressure
* Urine output
* Hearing (especially with high doses or prolonged therapy)
* Blood glucose (in diabetic patients)
* Uric acid
## Clinical Pearls
* Furosemide is a potent diuretic; monitor fluid and electrolyte balance closely, especially in the elderly and those with significant renal or hepatic impairment.
* Administer oral furosemide with food or milk to minimize gastric upset.
* Intravenous furosemide should be administered slowly (e.g., over 30-60 minutes) to reduce the risk of ototoxicity. Rapid IV push can lead to transient deafness.
* Correct electrolyte imbalances and dehydration before initiating or during therapy.
* Patients with edema may require higher doses than those treated for hypertension.
* The dose and frequency of administration should be individualized based on the patient's response and tolerance.
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*Please verify the current prescribing information for complete details before initiating therapy.*
