Diuretics
Diuretics are a class of medications that increase urine output by promoting the excretion of water and electrolytes from the kidneys. They are used to treat hypertension, heart failure, kidney disorders, and fluid overload conditions.
Classification of Diuretics
- Osmotic Diuretics
- Mannitol, Sorbitol
- Carbonic Anhydrase Inhibitors
- Acetazolamide
- Loop Diuretics
- Furosemide, Torsemide
- Thiazide Diuretics
- Hydrochlorothiazide, Chlorthalidone
- Potassium-Sparing Diuretics
- Aldosterone Antagonists: Spironolactone
- Sodium Channel Blockers: Amiloride
Pharmacodynamics (Mechanism of Action)
- Osmotic Diuretics (Mannitol, Sorbitol)
- Increase osmolarity of the glomerular filtrate, preventing water reabsorption.
- Promote water excretion without significant sodium loss.
- Reduce intracranial & intraocular pressure.
- Carbonic Anhydrase Inhibitors (Acetazolamide)
- Inhibit carbonic anhydrase in the proximal tubule, reducing bicarbonate (HCO₃⁻) reabsorption.
- Increase excretion of bicarbonate, sodium, and water → Alkaline urine.
- Can cause metabolic acidosis due to HCO₃⁻ loss.
- Loop Diuretics (Furosemide, Torsemide)
- Inhibit Na⁺/K⁺/2Cl⁻ cotransporter in the ascending loop of Henle.
- Decrease sodium, potassium, chloride reabsorption → Strong diuresis.
- Reduce preload & afterload in heart failure.
- Most potent diuretics.
- Thiazide Diuretics (Hydrochlorothiazide, Chlorthalidone)
- Inhibit Na⁺/Cl⁻ symporter in the distal convoluted tubule.
- Mild-moderate diuresis, used mainly for hypertension.
- Cause calcium retention (↓ Risk of kidney stones & osteoporosis).
- Potassium-Sparing Diuretics
- Aldosterone Antagonists (Spironolactone):
- Block aldosterone receptors, preventing sodium reabsorption & potassium excretion.
- Used in heart failure & hyperaldosteronism.
- Sodium Channel Blockers (Amiloride):
- Block sodium channels in distal tubules & collecting ducts.
- Reduce sodium reabsorption & prevent potassium loss.