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Pharmacology · single question

What is the mechanism of action of thiazide diuretics and their key dental side effect?

  1. Block Na-K-2Cl transporter in loop of Henle → hypokalemia + ototoxicity
  2. Block Na-Cl cotransporter in distal convoluted tubule → hypokalemia + xerostomia
  3. Inhibit aldosterone receptors → hyperkalemia
  4. Inhibit carbonic anhydrase → metabolic acidosis
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Correct answer: B. Block Na-Cl cotransporter in distal convoluted tubule → hypokalemia + xerostomia

Thiazide diuretics (hydrochlorothiazide, chlorthalidone) block the Na-Cl cotransporter in the distal convoluted tubule, reducing sodium and water reabsorption. Key side effects: hypokalemia, hyperuricemia, hyperglycemia, hypercalcemia. Dental relevance: XEROSTOMIA — dry mouth increases cervical caries risk.
  • A. ❌ Na-K-2Cl transporter blockade is the mechanism of LOOP diuretics (furosemide), not thiazides.
  • B. ✅ Thiazides block Na-Cl cotransporter in distal tubule → hypokalemia + xerostomia (dental relevance).
  • C. ❌ Aldosterone receptor blockade = spironolactone (potassium-sparing) → hyperkalemia.
  • D. ❌ Carbonic anhydrase inhibition = acetazolamide → metabolic acidosis.

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