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1. Diuretics
PREPARED BY : DR M YOUNAS

3.  Definition : Drugs that increase the excretion of water and electrolytes from the
body by enhancing urine output.
 General function
 Reduce extracellular fluid volume
 Lower blood pressure
 Relieve edema

4. Classification (MOA-based)
 Carbonic anhydrase inhibitors
 Osmotic diuretics
 Loop diuretics
 Thiazide diuretics
 Potassium sparing diuretics

6. Carbonic Anhydrase Inhibitors
(CAIs)
 Example : Acetazolamide
 Site of action : Proximal tubules
 MOA : MOA: Inhibit carbonic anhydrase → ↓ H secretion → ↓ Na
⁺ ⁺
reabsorption → ↑ HCO and water loss
₃⁻
 Clinical uses:
 Glaucoma (↓ aqueous humor production)
 Acute mountain sickness (↓ CSF production)
 Metabolic alkalosis
 Side effects: Metabolic acidosis, blurred vision, hypokalemia,
paresthesia

7. Osmotic Diuretics
 Example: Mannitol (IV only)
 Site of action: Proximal tubule & descending loop of Henle
 MOA: Inert substance → increases osmotic pressure → prevents
water reabsorption
 Clinical uses:
 Cerebral edema
 Acute glaucoma
 Oliguric acute renal failure
 Side effects: Pulmonary edema (in CHF), dehydration,
hypernatremia

8. Loop Diuretics
 Examples: Furosemide, Bumetanide, Torsemide
 Site of action: Thick ascending limb of loop of Henle
 MOA: Inhibit Na -K -2Cl cotransporter → very strong diuresis → loss of Na , K , Cl ,
⁺ ⁺ ⁻ ⁺ ⁺ ⁻
Ca² , Mg²
⁺ ⁺
 Clinical uses:
 Pulmonary edema (fast action)
 CHF with volume overload
 Hypertension (when resistant to thiazides)
 Hypercalcemia (promotes Ca² loss)
⁺
 Side effects: Hypokalemia, hypocalcemia, metabolic alkalosis, ototoxicity, gout
(↑ uric acid)

9. Thiazide Diuretics
 Examples: Hydrochlorothiazide, Chlorthalidone, Indapamide
 Site of action: Distal convoluted tubule
 MOA: Inhibit Na -Cl symporter → moderate diuresis → retain Ca²
⁺ ⁻ ⁺
 Clinical uses:
 First-line in hypertension
 CHF (mild)
 Nephrogenic diabetes insipidus (↓ urine volume)
 Prevention of kidney stones (↓ Ca² excretion)
⁺
 Side effects: Hypokalemia, hyponatremia, hyperglycemia, hyperlipidemia,
hyperuricemia (gout), hypercalcemia

10. Potassium-Sparing Diuretics
 Examples:
Spironolactone, Eplerenone (aldosterone antagonists) Amiloride, Triamterene
(ENaC blockers)
 Site of action: Collecting duct
 MOA:
Block aldosterone receptors (spironolactone)
Or block Na channels (amiloride, triamterene) → ↓ Na reabsorption & ↓ K
⁺ ⁺ ⁺
secretion
 Clinical uses:
 CHF (↓ mortality with spironolactone)
 Resistant hypertension
 Primary hyperaldosteronism
 Side effects: Hyperkalemia, metabolic acidosis, gynecomastia (spironolactone)

11. General Clinical Uses of Diuretics
 Hypertension (thiazides = first-line)
 Congestive heart failure (loops, K -sparing)
⁺
 Renal diseases with edema (loops)
 Cirrhosis with ascites (spironolactone)
 Glaucoma (acetazolamide, mannitol)
 Raised intracranial pressure (mannitol)

12. Thank You