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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium and chloride in the thick ascending limb of the loop of Henle, leading to increased excretion of water, sodium, chloride, potassium, hydrogen, calcium, and magnesium.
## Primary Indications
* Edema associated with congestive heart failure
* Liver cirrhosis
* Renal disease (including nephrotic syndrome)
* Pulmonary edema (acute)
* Hypertension (adjunctive therapy)
## Adult Dosing
* **Edema:** Oral: 20-80 mg once daily, may increase by 20-40 mg every 6-8 hours as needed. Usual maintenance dose: 40-80 mg once daily or divided twice daily. Maximum oral dose: 600 mg/day (higher doses may be used in severe cases under close supervision).
* **Acute Pulmonary Edema:** IV: 20-40 mg. If no adequate response within 1 hour, may administer another 40 mg IV. Subsequent doses typically 20-40 mg every 4-6 hours.
* **Hypertension:** Oral: 40 mg twice daily (usually in combination with other antihypertensives).
## Pediatric Dosing
* **Edema/Hypertension:** Oral: 1-2 mg/kg/dose once daily, may increase every 6 hours. Maximum dose: 6 mg/kg/day.
* **Edema/Hypertension:** IV/IM: 1 mg/kg/dose, may increase by 1 mg/kg every 2 hours. Maximum dose: 6 mg/kg/day.
* **Infants (<30 days):** IV/IM: 0.5 mg/kg/dose.
## Dose Adjustments
* **Renal Impairment:** May require higher doses due to reduced GFR and impaired tubular secretion. Closely monitor fluid and electrolyte balance.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides (possible cross-sensitivity)
## Adverse Effects
* **Electrolyte Imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and Hypotension:** Especially with rapid IV administration or excessive diuresis.
* **Ototoxicity:** Hearing impairment, tinnitus (more common with rapid IV infusion and high doses).
* **Hyperglycemia and Hyperuricemia:** Can precipitate gout.
* **Photosensitivity.**
* **Aplastic anemia, agranulocytosis, thrombocytopenia** (rare but serious).
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May reduce diuretic and antihypertensive effect.
* **ACE Inhibitors/ARBs/Diuretics:** Increased risk of severe hypotension and electrolyte imbalances.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, increased risk of lithium toxicity.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Serum electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Blood pressure
* Fluid balance (intake and output)
* Hearing (especially with high doses or rapid IV administration)
* Blood glucose and uric acid levels (in susceptible patients)
## Clinical Pearls
* Administer oral doses with food or milk to minimize GI upset.
* IV administration should be slow (e.g., 30-60 minutes) to reduce the risk of ototoxicity and hypotension.
* Correct significant electrolyte abnormalities before initiating or adjusting furosemide therapy.
* For chronic heart failure, initiating furosemide at a lower dose and titrating slowly based on symptom response and weight changes can minimize adverse effects.
Please verify current prescribing information with the most recent official drug monograph or institutional protocol before initiating therapy.
