1. What are diuretics?
Answer:
Diuretics are drugs that increase the rate of urine formation by promoting the excretion of sodium and water from the kidneys.
2. What are the major classes of diuretics?
Answer:
- Loop diuretics – e.g., Furosemide
- Thiazide diuretics – e.g., Hydrochlorothiazide
- Potassium-sparing diuretics – e.g., Spironolactone, Amiloride
- Carbonic anhydrase inhibitors – e.g., Acetazolamide
- Osmotic diuretics – e.g., Mannitol
3. Where do different diuretics act in the nephron?
Answer:
| Class | Site of Action |
|---|---|
| Loop diuretics | Thick ascending loop of Henle |
| Thiazides | Distal convoluted tubule |
| Potassium-sparing | Late distal tubule & collecting duct |
| Carbonic anhydrase inhibitors | Proximal tubule |
| Osmotic diuretics | Throughout nephron, esp. proximal tubule & loop |
4. What is the mechanism of action of loop diuretics?
Answer:
They inhibit the Na⁺-K⁺-2Cl⁻ co-transporter in the thick ascending limb of the loop of Henle, leading to loss of Na⁺, K⁺, Cl⁻, and water.
5. What are the common uses of loop diuretics?
Answer:
- Acute pulmonary edema
- Congestive heart failure
- Edema due to liver or kidney disease
- Hypertension (less common)
6. What are the side effects of loop diuretics?
Answer:
- Hypokalemia
- Hypocalcemia
- Ototoxicity
- Dehydration
- Hyperuricemia
7. What is the mechanism of thiazide diuretics?
Answer:
They inhibit the Na⁺-Cl⁻ symporter in the distal convoluted tubule.
8. What are thiazides used for?
Answer:
- First-line treatment for essential hypertension
- Mild to moderate heart failure
- Nephrolithiasis
- Nephrogenic diabetes insipidus
9. What are the adverse effects of thiazide diuretics?
Answer:
- Hypokalemic metabolic alkalosis
- Hyperglycemia
- Hyperuricemia
- Hyperlipidemia
- Hypercalcemia
- Mnemonic: "Hyper GLUC" – Glucose, Lipids, Uric acid, Calcium
10. What are potassium-sparing diuretics and how do they work?
Answer:
| Drug | Mechanism |
|---|---|
| Spironolactone | Aldosterone antagonist |
| Amiloride/Triamterene | ENaC sodium channel blockers |
11. When are potassium-sparing diuretics used?
Answer:
- To prevent hypokalemia
- Heart failure (spironolactone)
- Hyperaldosteronism
12. What are the side effects of potassium-sparing diuretics?
Answer:
- Hyperkalemia
- Spironolactone: Gynecomastia, menstrual irregularities
13. What is the role of carbonic anhydrase inhibitors?
Answer:
They inhibit carbonic anhydrase → decreased H⁺ secretion → less Na⁺ reabsorption → mild diuresis.
Uses: Glaucoma, altitude sickness, metabolic alkalosis, epilepsy
14. Side effects of carbonic anhydrase inhibitors?
Answer:
- Metabolic acidosis
- Hypokalemia
- Paresthesia
- Renal stones
15. How do osmotic diuretics work?
Answer:
They increase tubular fluid osmolarity → water retention → diuresis.
16. Uses of mannitol?
Answer:
- Cerebral edema
- Raised intracranial/intraocular pressure
- Acute renal failure (to maintain urine output)
17. Contraindications for mannitol?
Answer:
- Heart failure
- Severe dehydration
18. Common drug interactions with diuretics?
Answer:
- Loop + aminoglycosides → ototoxicity
- Diuretics + digoxin → digoxin toxicity
- Thiazides + lithium → lithium toxicity
19. What is diuretic resistance and how is it managed?
Answer:
Reduced response to diuretics.
Management: Higher doses, IV route, drug combination, address causes.
20. Table: Loop vs Thiazide vs K-sparing effects
| Electrolyte | Loop | Thiazide | K-sparing |
|---|---|---|---|
| Na⁺ | ↓ | ↓ | ↓ |
| K⁺ | ↓↓ | ↓ | ↑ |
| Ca²⁺ | ↓ | ↑ | - |
| H⁺ | ↓ | ↓ | ↑ (acidosis) |