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## Furosemide
### Overview
Furosemide is a potent loop diuretic used to reduce fluid overload in conditions such as heart failure, liver cirrhosis, and renal disease, and to manage hypertension.
### Primary Indications
* Edema associated with congestive heart failure (CHF), liver cirrhosis, and renal disease (including nephrotic syndrome).
* Hypertension (usually as adjunctive therapy).
### Adult Dosing
* **Edema:** The usual starting dose is 20-80 mg orally once daily. Doses may be increased by 20-40 mg every 6-8 hours as needed. Doses can be given once or twice daily. The maximum daily dose for oral administration is generally 600 mg, but higher doses may be used under close medical supervision in hospitalized patients.
* **Hypertension:** The usual starting dose is 40 mg orally twice daily. This dose may be adjusted based on response.
### Pediatric Dosing
* **Edema:**
* Oral: 1-4 mg/kg/dose once daily. Doses may be repeated every 6 hours as needed. The maximum daily dose is typically 40 mg, but higher doses may be used in hospitalized patients.
* Intravenous/Intramuscular: 1 mg/kg/dose. Doses may be repeated every 2 hours as needed. The maximum dose for a single administration is 20 mg. Higher doses may be used in hospitalized patients.
* **Neonates:** Higher doses may be required due to immature renal function. Consult specific neonatal protocols.
### Dose Adjustments
* **Renal Impairment:** Patients with severe renal impairment may require lower doses or less frequent administration due to prolonged half-life and risk of accumulation. However, sometimes higher doses are needed to achieve diuresis in the setting of renal failure. Careful titration is essential.
* **Hepatic Impairment:** Caution is advised due to the risk of electrolyte imbalances and hepatic encephalopathy. Doses may need to be reduced.
### Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
* Hepatic coma or severe electrolyte depletion.
### Adverse Effects
* **Electrolyte Imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and Hypotension:** Especially with rapid or excessive diuresis.
* **Ototoxicity:** Transient or permanent hearing loss, particularly with rapid IV administration or high doses, or in patients with renal impairment or concomitant ototoxic drug use.
* **Hyperglycemia:** Can occur, especially in diabetic patients.
* **Hyperuricemia:** Can precipitate gout.
* **Dizziness, lightheadedness, weakness.**
* **Photosensitivity.**
### Key Drug Interactions
* **Aminoglycosides and other Ototoxic Drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May reduce the diuretic and antihypertensive effects of furosemide and increase the risk of renal impairment.
* **Lithium:** Furosemide can decrease lithium clearance, increasing the risk of lithium toxicity.
* **Antihypertensives (including ACE inhibitors, ARBs, beta-blockers):** Additive hypotensive effects.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Hypokalemia induced by furosemide increases the risk of digoxin toxicity.
### Monitoring
* **Fluid and Electrolytes:** Serum electrolytes (sodium, potassium, chloride, magnesium, calcium), BUN, creatinine, and fluid balance (intake/output) should be monitored regularly, especially with high doses or prolonged therapy.
* **Blood Pressure:** Monitor for hypotension.
* **Hearing:** Assess for hearing impairment.
* **Blood Glucose:** Especially in diabetic patients.
* **Uric Acid:** Especially in patients with a history of gout.
### Clinical Pearls
* Furosemide is a potent diuretic; dose selection and titration are critical to avoid excessive fluid loss and electrolyte disturbances.
* Oral furosemide is generally effective for edema. Intravenous administration provides a more rapid onset of action for acute fluid overload.
* Rate of IV administration: Administer IV furosemide slowly (e.g., over 1-2 minutes) to minimize the risk of ototoxicity. Consider continuous infusion in critically ill patients.
* Oral bioavailability of furosemide can vary; switching between oral formulations or from IV to oral may require dose adjustments.
* Patients with heart failure may require higher doses than those with renal or hepatic disease.
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*This information is intended for healthcare professionals. Always consult the current prescribing information and relevant clinical guidelines before making treatment decisions.*
