What Are Diuretics?
Diuretics are medicines that increase urine output by acting directly on the kidneys. They help remove excess water and important electrolytes such as sodium (Na+), chloride (Cl−), and bicarbonate (HCO3−) from the body. The kidney functions of glomerular filtration, tubular secretion, and tubular reabsorption control urine formation. Diuretic drugs reduce tubular reabsorption of ions, resulting in increased urine formation.
Classification of Diuretics
- Carbonic Anhydrase Inhibitors: Acetazolamide, Methazolamide, Dichlorphenamide
- Thiazide Derivatives:
- Chlorothiazide & Analogues: Chlorothiazide, Benzthiazide
- Hydrochlorothiazide & Analogues: Hydrochlorothiazide, Hydroflumethiazide, Bendroflumethiazide, Trichlormethiazide, Methyclothiazide, Polythiazide, Cyclothiazide, Cyclopenthiazide
- Loop Diuretics: Furosemide, Bumetanide, Ethacrynic acid
- Potassium Sparing Diuretics: Amiloride, Triamterene, Spironolactone
- Osmotic Diuretics: Mannitol, Isosorbide, Glycerol, Urea
- Miscellaneous: Indapamide, Xipamide, Clopamide, Metolazone, Quinethazone, Chlorthalidone
Examples of Diuretics
Common medicines used in clinical practice include: Acetazolamide, Furosemide, Bumetanide, Chlorthalidone, Benzthiazide, Metolazone, Xipamide, Spironolactone.
Acetazolamide
Acetazolamide is the prototype drug of Carbonic Anhydrase Inhibitors. It blocks the carbonic anhydrase enzyme in kidney tubules, which prevents the exchange of hydrogen and sodium ions. This leads to increased excretion of sodium, potassium, and bicarbonate in urine, producing alkaline urine.
Uses
- Glaucoma (reduces eye pressure)
- Alkalinization of urine for UTIs and toxic drug removal
- Adjunct therapy in epilepsy
- Prevention of acute mountain sickness
Storage
Store below 25°C, protected from moisture and light.
Furosemide
Furosemide is a fast-acting loop diuretic that blocks the Na⁺–K⁺–2Cl⁻ transporter in the Loop of Henle. This prevents reabsorption of sodium and water, resulting in strong diuresis.
Uses
- Edema due to heart failure, liver cirrhosis, or kidney disease
- Control of hypertension (alone or combined with other drugs)
Storage
Store at 15–30°C and protect from moisture and light.
Bumetanide
Bumetanide is a strong loop diuretic used when patients do not respond to furosemide. It blocks chloride and sodium reabsorption in the Loop of Henle and enhances water excretion.
Uses
- Edema in heart failure, kidney disease, or liver cirrhosis
Chlorthalidone
Chlorthalidone is a long-acting thiazide-like diuretic widely used for hypertension. It blocks the Na⁺/Cl⁻ symporter in the renal tubules, promoting excretion of sodium, chloride, and water. It also increases potassium loss by enhancing sodium delivery to distal tubules.
Uses
- Edema in heart, liver, or kidney disease
- Long-term management of hypertension
Benzthiazide
Benzthiazide is a thiazide diuretic that inhibits Na⁺–Cl⁻ transporter in the distal tubule, increasing excretion of sodium, water, and potassium.
Uses
- Hypertension
- Edema associated with fluid retention
Metolazone
Metolazone is a thiazide-like agent that inhibits sodium reabsorption in the cortical diluting segment. It is commonly used in resistant edema and hypertension.
Uses
- Heart failure and nephrotic syndrome edema
- Hypertension management
Xipamide
Xipamide increases sodium and potassium loss and reduces calcium excretion. It is useful in treating swelling and high blood pressure.
Uses
- Hypertension
- Edema
Spironolactone
Spironolactone is a potassium-sparing diuretic. It competitively blocks aldosterone receptors in the distal tubule, promoting sodium and water excretion while retaining potassium.
Uses
- Refractory edema in heart failure, cirrhosis, or nephrotic syndrome
- Treatment of hypokalaemia and Conn’s syndrome
- Useful in low-renin hypertension
