ICU · pharmacology

ICU Diuretics Pharmacology — Comprehensive (Loop, Thiazide, K-Sparing, Acetazolamide)

Also known as Loop diuretics · Furosemide · Bumetanide · Torasemide · Thiazide diuretics · Chlorthalidone · Metolazone · Spironolactone · Eplerenone · Amiloride · Acetazolamide · Sequential nephron blockade · Diuretic resistance · DOSE trial · RALES trial

ICU diuretics — comprehensive pharmacology organised by SITE OF ACTION in the nephron. The four classes map onto four sequential segments: PROXIMAL TUBULE → acetazolamide (carbonic anhydrase inhibitor — weak — HCO3 loss → metabolic acidosis); THICK ASCENDING LIMB of the loop of Henle → loop diuretics (furosemide/bumetanide/torasemide — block the Na-K-2Cl [NKCC2] cotransporter — the MOST POTENT class — NKCC2 reabsorbs up to 25% of filtered salt); DISTAL CONVOLUTED TUBULE → thiazides (hydrochlorothiazide/chlorthalidone/metolazone — block the Na-Cl [NCC] cotransporter); CORTICAL COLLECTING DUCT → potassium-sparing diuretics (either aldosterone-receptor antagonists — spironolactone/eplerenone [RALES trial — 30% mortality reduction in severe HFrEF] — or the epithelial Na+ channel [ENaC] blockers — amiloride/triamterene). Clinical uses: loop (pulmonary oedema, heart failure decongestion, AKI fluid overload); thiazide (hypertension, heart failure, nephrogenic DI, hypercalciuria); K-sparing (HFrEF with spironolactone, Conn syndrome, cirrhotic ascites, diuretic-induced hypokalaemia); acetazolamide (metabolic alkalosis correction, altitude sickness, glaucoma, CSF production). Adverse-effect signature by class: loop → HYPOkalaemia, hypomagnesaemia, HYPOcalcaemia, ototoxicity (high-dose IV push), hyperuricaemia, contraction alkalosis; thiazide → HYPOkalaemia, HYPOnatraemia, hyperuricaemia, HYPERcalcaemia (opposite to loop — classic exam contrast); K-sparing → HYPERkalaemia, metabolic acidosis, gynaecomastia (spironolactone — antiandrogen effect); acetazolamide → metabolic acidosis, hypokalaemia, renal stones. SEQUENTIAL NEPHRON BLOCKADE (loop + thiazide) is the key strategy for RESISTANT OEDEMA / diuretic resistance. The DOSE trial established that continuous infusion and intermittent bolus furosemide have equivalent efficacy and renal safety.

Checked against its sources on 3 Sept 2026