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## Furosemide (Lasix)
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, liver cirrhosis, and renal disease, including in patients on dialysis. It is also used to treat hypertension, although it is not a first-line agent for this indication.
### Primary Indications
* Edema due to heart failure
* Edema due to liver cirrhosis
* Edema due to renal disease
* Hypertension (adjunct therapy)
### Adult Dosing
* **Edema:**
* Oral: 20 mg to 80 mg once daily. The dose may be increased by 20 mg to 40 mg every 6 to 8 hours as needed until desired response is achieved. The maximum daily dose is typically 600 mg, but doses up to 1 g/day have been used in severe cases under close supervision.
* Intravenous (IV) or Intramuscular (IM): 20 mg to 40 mg once daily. If a greater response is needed, the dose may be increased by 20 mg every 2 hours or by 40 mg every 4 hours. Continuous IV infusion may be considered in severe cases. Maximum daily dose generally 600 mg, but higher doses may be required in specific situations.
* **Hypertension:**
* Oral: 40 mg twice daily.
### Pediatric Dosing
* **Edema:**
* Oral: 1 mg/kg to 2 mg/kg once daily, not to exceed 40 mg/day. If response is insufficient, the dose can be increased by 1 mg/kg to 2 mg/kg every 6 to 8 hours. Maximum daily dose is typically 6 mg/kg/day.
* IV/IM: 1 mg/kg once daily, not to exceed 20 mg/dose. If response is insufficient, the dose can be increased by 1 mg/kg every 2 hours. Maximum daily dose typically 6 mg/kg/day.
### Dose Adjustments
* **Renal Impairment:** In patients with significant renal impairment, higher doses may be required due to reduced drug bioavailability and altered sensitivity. Close monitoring of response and electrolytes is crucial.
* **Hepatic Impairment:** Caution is advised. Furosemide can precipitate hepatic encephalopathy.
### Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides
### Adverse Effects
* **Electrolyte Imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration:** Particularly in the elderly.
* **Ototoxicity:** Hearing loss (often reversible) especially with rapid IV administration or in patients with renal impairment or receiving other ototoxic drugs.
* **Hypotension:** Especially with IV administration.
* **Hyperglycemia:**
* **Hyperuricemia:** May precipitate gout.
* **Photosensitivity:**
### Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **Antihypertensives:** Additive hypotensive effect.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May reduce diuretic and antihypertensive effects, and increase risk of renal impairment.
* **Lithium:** Reduced lithium clearance, increasing lithium toxicity risk.
* **_cis_-platin:** Increased risk of ototoxicity and nephrotoxicity.
### Monitoring
* **Electrolytes:** Serum electrolytes (sodium, potassium, chloride, magnesium, calcium) and fluid status, especially with initiation, dose changes, or in patients with risk factors.
* **Renal Function:** Serum creatinine and BUN.
* **Blood Pressure:**
* **Urine Output:**
* **Hearing:** Report any tinnitus or hearing impairment.
### Clinical Pearls
* Furosemide is a potent diuretic; its efficacy is dose-dependent.
* Oral administration can be less predictable than IV in patients with severe edema or malabsorption.
* When given IV, infuse slowly (over 30-60 minutes) to reduce the risk of ototoxicity.
* For patients requiring continuous diuresis, a continuous IV infusion may be more effective and less likely to cause electrolyte disturbances than intermittent dosing.
* In patients with congestive heart failure, concomitant administration with ACE inhibitors or ARBs can enhance diuresis and blood pressure control but increases the risk of hypotension and renal dysfunction; monitor closely.
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*Please consult the most current prescribing information for complete details and to confirm dosing and safety information.*
