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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