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# Furosemide
## Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, liver disease, 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, cirrhosis, renal disease)
* Hypertension
## Adult Dosing
* **Edema:**
* Oral: 20-80 mg once daily initially. If a greater diuresis is required, doses may be increased by 20-40 mg every 6-8 hours. The usual maintenance dose is 20-80 mg daily. Doses up to 600 mg daily have been used in severe cases under close supervision.
* Intravenous (IV) or Intramuscular (IM): 20-40 mg once daily. If inadequate response, may increase by 20 mg every 2 hours. Doses up to 100 mg once daily may be needed in severe edema.
* Intermittent IV infusion: 20-100 mg over 30-60 minutes.
* Continuous IV infusion: 4 mg/hour initially, may increase by 1-2 mg/hour every 2 hours based on response.
* **Hypertension:**
* Oral: 40 mg twice daily.
* **Maximum dose:** There is no absolute maximum dose, but doses exceeding 600 mg daily for edema require careful monitoring due to increased risk of adverse effects.
## Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose once daily. If inadequate response, may increase by 1 mg/kg/dose every 6-8 hours. Do not exceed 6 mg/kg/dose.
* IV/IM: 1 mg/kg/dose once daily. If inadequate response, may increase by 1 mg/kg/dose every 2 hours. Do not exceed 6 mg/kg/dose.
* **Neonates:** May be more sensitive to effects and require lower doses. Specific dosing should be guided by neonatology protocols.
## Dose Adjustments
* **Renal Impairment:** Furosemide is renally excreted; dose reduction may be necessary in severe renal impairment. However, high doses may be required to achieve diuresis in some patients with renal insufficiency.
* **Hepatic Impairment:** Monitor for electrolyte imbalances and fluid status closely.
## Contraindications
* Anuria
* Known hypersensitivity to furosemide or sulfonamides (cross-sensitivity possible).
* Severe electrolyte depletion (e.g., hypokalemia, hyponatremia).
## Adverse Effects
* **Common:** Dizziness, lightheadedness, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), dehydration, orthostatic hypotension, increased urination, hyperuricemia (may precipitate gout).
* **Less Common/Serious:** Ototoxicity (especially with rapid IV administration or high doses, potentially irreversible), pancreatitis, cholestatic jaundice, hepatic encephalopathy, blood dyscrasias (agranulocytosis, aplastic anemia), hyperglycemia, rash.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **NSAIDs:** May reduce diuretic and antihypertensive effect of furosemide and increase risk of nephrotoxicity.
* **Other ototoxic drugs (e.g., cisplatin):** Increased risk of ototoxicity.
* **Lithium:** Reduced renal clearance, increased risk of lithium toxicity.
* **Antihypertensives (including ACE inhibitors, ARBs, beta-blockers):** Additive hypotensive effect.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* **Electrolytes:** Serum sodium, potassium, chloride, magnesium, calcium.
* **Renal function:** BUN, serum creatinine.
* **Fluid status:** Daily weights, intake/output.
* **Blood pressure:** Especially with concomitant antihypertensives.
* **Hearing:** Advise patients to report tinnitus or hearing loss.
* **Blood glucose:** In diabetic patients.
* **Uric acid:** In patients with a history of gout.
## Clinical Pearls
* Administer oral furosemide with or without food.
* Oral administration is generally preferred for chronic management.
* IV administration is typically reserved for patients who cannot take oral medications or require a rapid onset of action.
* Rapid IV administration (e.g., bolus injection) can increase the risk of ototoxicity. Administer IV doses over at least 30-60 minutes or as a continuous infusion when using higher doses.
* Be aware of the potential for rebound edema when discontinuing furosemide.
* Electrolyte and fluid status should be monitored closely, especially in elderly patients, those with significant renal or hepatic impairment, and those receiving other diuretics or medications that affect electrolytes.
* In patients with severe renal impairment, a continuous infusion may be more effective than intermittent boluses.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols for complete and up-to-date guidance.
