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## Furosemide (Lasix)
### Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) and high blood pressure.
### Primary Indications
* Edema associated with congestive heart failure (CHF), liver cirrhosis, and renal disease.
* Hypertension (often in combination with other antihypertensives).
* Acute pulmonary edema.
### Adult Dosing
* **Edema:** Initial dose: 20-80 mg orally once daily. Doses may be increased by 20-40 mg every 6-8 hours as needed, or doses can be divided. Usual maintenance dose: 40-80 mg orally once or twice daily. Maximum oral dose: 600 mg daily (higher doses rarely needed and may increase risk).
* **Hypertension:** Initial dose: 40 mg orally twice daily. Doses may be adjusted based on response. Usually not recommended as monotherapy for hypertension.
* **Acute Pulmonary Edema:** Initial dose: 40 mg IV once. If inadequate response, a second dose of 80 mg IV can be given 2 hours later. Further doses based on response.
### Pediatric Dosing
* **Edema/Hypertension:**
* Oral: 1-2 mg/kg/dose orally once daily. If inadequate response, increase dose by 1-2 mg/kg/dose every 6-8 hours. Maximum dose: 6 mg/kg/day.
* IV: 1 mg/kg/dose IV once. If inadequate response, may increase by 1 mg/kg/dose every 2 hours. Maximum dose: 6 mg/kg/day.
### Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in patients with renal impairment due to decreased renal excretion and potential for accumulation. However, caution is advised as high doses can be nephrotoxic.
* **Hepatic Impairment:** Monitor closely due to potential for electrolyte imbalances and hepatic encephalopathy.
### Contraindications
* Anuria.
* History of hypersensitivity to furosemide or sulfonamides.
### Adverse Effects
* **Electrolyte disturbances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration.**
* **Ototoxicity:** Especially with rapid IV administration or high doses.
* **Hyperuricemia:** Can precipitate gout.
* **Hyperglycemia.**
* **Orthostatic hypotension.**
### Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May reduce diuretic and antihypertensive effects.
* **Lithium:** Increased risk of lithium toxicity due to decreased renal excretion.
* **Antihypertensives (including ACE inhibitors, ARBs, beta-blockers):** Additive hypotensive effect.
* **Corticosteroids:** Increased risk of hypokalemia.
### Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium) - especially during initiation and dose changes.
* Renal function (BUN, creatinine).
* Fluid status (weight, edema, urine output).
* Blood pressure.
* Blood glucose (in diabetic patients).
* Uric acid levels (especially in patients with gout).
### Clinical Pearls
* Administer IV furosemide slowly (over 30-60 minutes) to reduce the risk of ototoxicity. Rapid IV push is generally not recommended.
* Oral furosemide is typically taken in the morning to minimize nocturia. If a second dose is needed, it should be taken at least 4-6 hours before bedtime.
* Be aware of potassium-depleting effects and counsel patients on dietary potassium intake or consider potassium supplementation if indicated.
* Monitor for signs of dehydration and electrolyte imbalance (dizziness, weakness, muscle cramps).
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*Please verify this information with the most current prescribing information and relevant institutional protocols.*
