Description
Diuretics - Advanced Diuresis
• Loop diuretics have a sigmoidal dose-response curve so double dose until adequate response is achieved
• If respiratory distress in patient w/ unknown history, start with furosemide 20-40mg IV and double Q1H until response (may need higher doses if impaired renal function)
• Daily standing weights, Na+ restriction 2g/day, consider fluid restriction (esp. if HypoNa)
• Loop + thiazide → sequential nephron blockade (counteracts natural ↑ in DCT Na reabsorption from loop diuretics); use if refractory edema; monitor for ↓K+, ↓Mg2+, ↓bicarb
Thiazide Diuretics:
• Chlorthalidone*, HCTZ, metolazone, chlorothiazide (IV/PO)
• Inhibit NaCl channel in DCT to ↓ Na reabsorption and prevent urinary dilution (avoid if SIADH); no effect on medullary concentrating gradient
• Administer 30 min before loop diuretic to “disable” DCT (use PO metolazone, IV chlorothiazide)
• AE: ↓ Na+, ↓ K+, ↓ Mg2+, ↑ Ca2+, ↑ urate, HLD, pancreatitis
• Try metolazone 2.5-10mg PO before chlorothiazide 500-1000mg IV ($$$)
Loop Diuretics:
• Furosemide, Torsemide, Bumetanide
• Inhibit Na-K-2Cl transporter in ascending limb of loop of Henle to ↓
• Na reabsorption and “break” medullary concentrating gradient (unable to concentrate urine)
• AE: ↓ K+, ↓ Mg2+, ↓ Ca2+, ↑ urate, ↑ HCO3-, ototoxicity, allergy
- Consider dosing BID-QID to avoid antinatriuresis seen in QD dosing
- If severe sulfa allergy, consider ethacrynic acid (50mg PO = furosemide 40mg PO)
Carbonic anhydrase inhibitors: acetazolamide 250-1000mg PO QD, can do TID x1d vs QD x3d for metabolic alkalosis (pH > 7.6)
Aldosterone antagonists: spironolactone 25-200mg QD-BID, eplerenone 25-50mg QD-BID, mortality benefit in class II-IV HFrEF
• ↑ K, gynecomastia (10%, only spironolactone)
• Epleronone has greater aldosterone receptor selectivity but more expensive
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