2008A02 List the classes of drugs that are useful in inducing diuresis clinically. Outline their mechanism of action.

Group

Drug

Site of action

Mechanism of action

Osmotic diuretic
(can be profound)

Mannitol

Whole nephron

↓Passive reabsorption of water

Carbonic anhydrase inhibitor

Acetazolamide

Proximal tubule

↓Na⁺/H⁺ antiport activity

↓HCO₃^- reabsorption, NAGMA

Loop diuretic

(MOST POTENT)

Frusemide

Bumetanide

Thick ascending loop of Henle

Inhibit apical Na⁺K⁺2Cl^- symporter

(Compensatory ↑Na⁺/K⁺ antiport in distal nephron -> ↓K⁺)

Thiazide

Hydrochlorothiazide

Bendoflumethiazide

Distal convoluted tubule

Inhibit DT Na⁺/Cl^- symporter

(Compensatory ↑Na⁺/K⁺ antiport in distal nephron -> ↓K⁺)

MRA “K⁺ sparing”

Spironolactone

Eplerenone

Connecting tubule

Collecting ducts

Inhibit mineralocorticoid receptor

Principal cell:

-↓Activity basolateral Na⁺K⁺ATPase

-↓Activity apical ENaC and ROMK

Type A intercalated cell:

-↓Activity apical H⁺ ATPase

ENaC inhibitor “K⁺ sparing”

Amiloride

Triamterene

Connecting tubule

Collecting ducts

Inhibit ENaC