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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, liver cirrhosis, and renal disease, including nephrotic syndrome. It is also used to treat hypertension, alone or in combination with other antihypertensives.
## Primary Indications
* Edema (congestive heart failure, liver disease, renal disease)
* Hypertension
## Adult Dosing
* **Edema:**
* Oral: Start with 20-80 mg once daily. The dose can be increased by 20-40 mg every 6-8 hours as needed. Maximum dose is typically 600 mg/day, but doses up to 200 mg have been used in severe cases under close supervision. Doses are often adjusted to achieve a target weight loss of 1-2 kg/day.
* Intravenous (IV)/Intramuscular (IM): Start with 20-40 mg once daily. If response is inadequate, subsequent doses may be increased by 20 mg every 2 hours. Maximum dose is typically 600 mg/day.
* **Hypertension:**
* Oral: 40 mg twice daily. Doses may be adjusted based on response. Not generally recommended as first-line therapy for hypertension unless edema is also present.
* **Continuous IV Infusion for Edema:**
* Loading dose: 80 mg IV.
* Maintenance infusion: 10 mg/hour. Doses can be adjusted based on urine output and electrolyte status.
## Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose every 6-12 hours. Maximum dose is 6 mg/kg/day.
* IV/IM: 1 mg/kg/dose every 6-12 hours. Maximum dose is 6 mg/kg/day.
* **Hypertension:** Dosing is not well-established in children and should be managed by a specialist.
## Dose Adjustments
* **Renal Impairment:** Patients with severe renal impairment may require lower doses due to increased sensitivity. Conversely, diuretic resistance can occur in severe renal failure, potentially requiring higher doses or continuous infusion.
* **Hepatic Impairment:** Use with caution; dose adjustments may be needed.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides
## Adverse Effects
* **Electrolyte imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and hypotension.**
* **Ototoxicity:** Particularly with rapid IV administration or high doses.
* **Hyperglycemia, hyperuricemia (gout).**
* **Photosensitivity.**
* **Rash, Stevens-Johnson syndrome (rare).**
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May reduce furosemide's natriuretic effect.
* **Lithium:** Increased risk of lithium toxicity.
* **Antihypertensives (e.g., ACE inhibitors, ARBs, beta-blockers):** Additive hypotensive effect.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
## Monitoring
* Serum electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Fluid balance (intake and output)
* Weight
* Blood pressure
* Blood glucose and uric acid (in susceptible patients)
* Auditory function (especially with high doses or rapid IV administration)
## Clinical Pearls
* Furosemide has a rapid onset of action (oral: ~1 hour; IV: ~5 minutes).
* Administer IV furosemide slowly (over 30-60 minutes) to reduce the risk of ototoxicity and hypotension.
* For patients with diuretic resistance, consider increasing the dose, administering via continuous infusion, or combining with a thiazide diuretic (if renal function permits).
* Oral potassium supplements or potassium-sparing diuretics may be needed to counteract hypokalemia.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant literature before making clinical decisions. Local protocols may dictate specific dosing or management strategies.*
