====== Furosemide (Lasix®) ======
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|^ Furosemide || Brand Names | Lasix® || Drug Class | Loop Diuretic || Primary Indications | Heart Failure; Pulmonary edema; Volume overload; CKD edema || Blood Pressure Effect | ↓ preload, ↓ BP || Mortality Benefit | No (symptom relief) || Elimination | Renal || Black Box Warning | Ototoxicity (high dose/rapid IV) || FDA Approval | 1966 |
===== Overview =====Furosemide is a potent loop diuretic that blocks NKCC2 in the thick ascending limb, producing brisk natriuresis and diuresis. It is first-line for acute decompensated heart failure and volume overload.
—-===== Mechanism of Action =====Primary Molecular Target * Na-K-2Cl cotransporter (NKCC2) in thick ascending limbSegment Effects * ↓ NaCl reabsorption in TAL * ↑ Ca2+ and Mg2+ excretion * Disrupts medullary concentrating gradientNet Physiologic Outcomes * Powerful diuresis * ↓ preload and pulmonary congestion * Rapid symptom relief in volume overload—-===== Indications ===== * Acute pulmonary edema * Decompensated heart failure * Edema in CKD/cirrhosis/nephrotic syndrome * Severe hypertension with volume overload—-
===== Black Box Warning =====Risk of profound diuresis, electrolyte depletion, and ototoxicity with high doses or rapid IV administration.
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===== Contraindications =====Absolute: * Anuria * Severe sulfonamide allergy (rare)Relative / Caution: * Hypovolemia * Severe electrolyte depletion * Gout
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===== Dosing =====Heart failure/edema: * PO: 20–80 mg daily or BID (titrate) * IV: 20–40 mg, repeat as neededRenal adjustment: * Higher doses often required in CKD
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===== Pharmacokinetics =====Absorption: * Oral/IVBioavailability: * ~50% (variable)Metabolism: * Minimal hepaticHalf-life: * ~2 hoursElimination: * Renal
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===== Adverse Effects =====Common: * Hypokalemia * Hypomagnesemia * Polyuria * HypotensionSerious: * Ototoxicity * AKI from overdiuresis * Hyponatremia
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===== Drug Interactions =====Increased risk: * Digoxin toxicity (via hypokalemia) * NSAIDs (↓ diuretic effect) * Lithium (↑ levels)Avoid combination: * Aminoglycosides (ototoxicity risk)
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===== Monitoring =====Labs: * Electrolytes (K+, Mg2+, Na+) * CreatinineVitals: * Blood pressure * WeightClinical: * Volume status * Hearing changes (high dose)
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===== Clinical Pearls ===== * Most potent class of diuretics * Useful in acute pulmonary edema * Causes hypocalcemia (unlike thiazides)
—-===== Comparison Within Class =====Compared to other loop diuretics: * Shorter half-life than torsemide * Variable oral bioavailability * Rapid onset when IV—-===== Related ===== * Loop Diuretics * Heart Failure * Diuretics