The reasoning: a diuretic's power equals the load it blocks — minus downstream compensation
| Class | Site / target | Peak FENa | K⁺ | Ca²⁺ | Mg²⁺ | Acid–base | Key uses / cautions |
|---|---|---|---|---|---|---|---|
| Carbonic anhydrase inhibitor (acetazolamide) | PCT, CA | ~3–5% | ↓ | — | — | acidosis | altitude sickness, glaucoma, IIH, metabolic alkalosis |
| Osmotic (mannitol) | PCT, loop (water) | — | ↓ | — | — | — | raised ICP; can precipitate pulmonary oedema |
| Loop (furosemide, bumetanide, torsemide) | TAL, NKCC2 | ~20–25% | ↓↓ | ↑ urine | ↑ urine | alkalosis | oedema, pulmonary oedema, hypercalcaemia; ototoxicity |
| Thiazide (HCTZ, chlorthalidone, indapamide) | DCT, NCC | ~5–8% | ↓ | ↓ urine | ↑ urine | alkalosis | hypertension, calcium stones, nephrogenic DI; hyponatraemia, hyperuricaemia, hyperglycaemia |
| K⁺‑sparing — MR antagonists (spironolactone, eplerenone, finerenone) | CNT/CCD, MR | ~2–3% | ↑ | — | — | acidosis | HFrEF, hyperaldosteronism, cirrhotic ascites, diabetic CKD (finerenone) |
| K⁺‑sparing — ENaC blockers (amiloride, triamterene) | CNT/CCD, ENaC | ~2–3% | ↑ | — | ↓ urine | acidosis | Liddle, lithium‑induced DI, adjunct |
| SGLT2 inhibitors | PCT, SGLT2 | modest | ~neutral | — | — | — | HF, CKD, diabetes |
| Vaptans | CD, V2 | aquaresis | — | — | — | — | hyponatraemia (specialist) |