Question
Compare the Mechanism of action, uses and adverse effects of Thiazides and Loop
diuretics.
Q4 8 marks Short Essays ★ ✓
Answer
Feature Thiazides Loop diuretics Site of action Distal convoluted tubule Thick ascending limb of loop of Henle Mechanism Inhibit Na⁺-Cl⁻ cotransporter Inhibit Na⁺-K⁺-2Cl⁻ (NKCC2) cotransporter Efficacy Moderate natriuresis (most Na⁺ already reabsorbed upstream) High-ceiling — marked natriuresis, even in renal impairment Calcium handling ↑Ca²⁺ reabsorption (hypercalcemia) ↑Ca²⁺ excretion (hypocalcemia) Uses Hypertension (first-line, especially elderly), mild edema, nephrogenic diabetes insipidus, hypercalciuria Acute pulmonary edema/heart failure, edema of cardiac/hepatic/renal origin, hyperkalemia, hypercalcemia Adverse effects Hypokalemia, hyponatremia, hyperglycemia, hyperuricemia, hyperlipidemia, hypercalcemia Hypokalemia, hyponatremia, hypochloremic metabolic alkalosis, ototoxicity, hyperuricemia, hypovolemia Example Hydrochlorothiazide Furosemide
Key distinguishing point : thiazides become ineffective once GFR falls significantly (limiting their use in advanced renal impairment), whereas loop diuretics retain efficacy even in reduced renal function — the reason loop diuretics, not thiazides, are the diuretic of choice in acute heart failure and significant renal impairment.
1 Renal Pharmacology
Other Years Asked
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3. It acts on the thick ascending limb of Loop of Henle
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