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# Furosemide
## Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, cirrhosis, and renal disease, as well as hypertension.
## Primary Indications
* Edema (congestive heart failure, liver cirrhosis, renal disease)
* Hypertension (often as adjunctive therapy)
## Adult Dosing
* **Edema:** Initial dose typically 20-80 mg orally once or twice daily. May increase by 20-40 mg every 6-8 hours as needed. Maximum daily dose generally 600 mg orally, though higher doses may be used in severe refractory edema under close supervision. Intravenous (IV) or intramuscular (IM) doses are usually twice the oral dose due to lower bioavailability.
* **Hypertension:** Initial dose typically 40 mg orally once or twice daily. Dosing is individualized based on response and concurrent antihypertensives. Maximum daily dose generally 40 mg orally for uncomplicated hypertension.
## Pediatric Dosing
* **Edema:** 1-4 mg/kg/dose orally every 6-12 hours. Maximum daily dose 40 mg orally. IV/IM dose is 1 mg/kg/dose, maximum 20 mg/dose. Higher doses may be required in premature infants or those with severe edema.
## Dose Adjustments
* **Renal Impairment:** Dose reduction may be necessary. In severe renal impairment, oral bioavailability may be reduced, and higher or IV doses may be required.
* **Hepatic Impairment:** Caution is advised. May require dose adjustment due to altered pharmacokinetics and risk of electrolyte imbalances.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides (cross-reactivity possible)
* Severe electrolyte depletion (e.g., hyponatremia, hypokalemia)
## Adverse Effects
* **Common:** Electrolyte disturbances (hypokalemia, hyponatremia, hypochloremia, metabolic alkalosis), dehydration, hypotension, dizziness, hyperuricemia, hyperglycemia.
* **Serious:** Ototoxicity (especially with rapid IV administration or high doses), severe allergic reactions, aplastic anemia, thrombocytopenia, pancreatitis.
## Key Drug Interactions
* **Aminoglycosides/Other Ototoxic Drugs:** Increased risk of ototoxicity.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May decrease diuretic and antihypertensive effects.
* **Lithium:** Reduced renal clearance of lithium, increasing lithium toxicity risk.
* **Antihypertensives:** Additive hypotensive effects.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* **Electrolytes:** Serum electrolytes (sodium, potassium, chloride) and fluid status (weight, urine output, signs of edema) should be monitored regularly, especially during initiation and dose changes.
* **Renal Function:** Serum creatinine and BUN.
* **Blood Pressure:** Monitor for hypotension.
* **Auditory Function:** Advise patients to report hearing changes.
* **Blood Glucose:** In diabetic patients.
## Clinical Pearls
* Oral bioavailability is variable (around 50-60%), and higher doses may be needed orally compared to IV/IM administration for equivalent effects.
* Rapid IV administration can lead to ototoxicity; infuse slowly (e.g., over 30-60 minutes).
* Electrolyte monitoring and replacement are crucial to prevent serious complications.
* For patients with significant edema, a continuous IV infusion or frequent dosing may be more effective than single daily doses.
* Dosing for refractory edema may require individual titration up to 600 mg/day orally or equivalent IV doses, guided by response and monitoring.
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*This information is intended for clinical decision-making and does not replace the need to consult the most current prescribing information, institutional protocols, and patient-specific factors.*
