Diuretics 

Fig. 01

Classification & MOA

Class	Example Drugs	Site of Action	Mechanism of Action (MOA)
1. Carbonic Anhydrase Inhibitors (CAI)	Acetazolamide, Dorzolamide	Proximal convoluted tubule (PCT)	Inhibits carbonic anhydrase → ↓ H⁺ secretion → ↓ Na⁺/H⁺ exchange → ↑ Na⁺, HCO₃⁻, water excretion
2. Loop Diuretics (High ceiling)	Furosemide, Bumetanide, Torsemide, Ethacrynic acid	Thick ascending loop of Henle	Inhibits Na⁺-K⁺-2Cl⁻ cotransporter → ↑ Na⁺, K⁺, Ca²⁺, Mg²⁺, water excretion
3. Thiazides	Hydrochlorothiazide, Chlorthalidone, Indapamide	Early distal convoluted tubule (DCT)	Inhibits Na⁺-Cl⁻ symporter → ↑ Na⁺, Cl⁻, water excretion; ↑ Ca²⁺ reabsorption
4. Potassium-Sparing Diuretics	a. Aldosterone antagonists: Spironolactone, Eplerenone b. Na⁺ channel blockers: Amiloride, Triamterene	Late distal tubule & collecting duct	a) Block aldosterone receptor → ↓ Na⁺ reabsorption, ↓ K⁺ excretion b) Block Na⁺ channels → prevent Na⁺ entry → ↓ K⁺ loss
5. Osmotic Diuretics	Mannitol, Glycerol, Isosorbide	PCT & descending loop of Henle	Increases osmotic pressure → prevents water reabsorption → ↑ water excretion
6. Vasopressin (ADH) Antagonists	Conivaptan, Tolvaptan	Collecting duct (V2 receptors)	Block ADH receptors → ↓ water reabsorption (aquaretics, not natriuretics)