Summer 25 - Diuretics

Question 1

What are diuretics?

Answer 1

Diuretics reduce plasma volume to lower blood pressure and are classically defined as agents that increase urine flow (water loss).

Question 2

What are natriuretics?

Answer 2

Natriuretics increase sodium excretion, leading to water loss.

Question 3

What are the categories of diuretics?

Answer 3

1. Osmotic
2. Carbonic anhydrase inhibitors
3. Thiazide and thiazide-like
4. Loop
5. Potassium-sparing

Question 4

What are the therapeutic uses of thiazides?

Answer 4

Thiazides are used for hypertension, congestive heart failure, renal calculi, nephrogenic diabetes insipidus, chronic renal failure (as adjunct), and osteoporosis.

Question 5

What are the therapeutic uses of loop diuretics?

Answer 5

Loop diuretics are used for hypertension, congestive heart failure, acute pulmonary edema, chronic or acute renal failure, nephrotic syndrome, and hyperkalemia.

Question 6

What are the therapeutic uses of potassium-sparing diuretics?

Answer 6

Potassium-sparing diuretics are used in chronic liver failure and congestive heart failure.

Question 7

What are the therapeutic uses of carbonic anhydrase inhibitors?

Answer 7

Carbonic anhydrase inhibitors are used in cystinuria (to alkalinize urine), glaucoma, acute altitude sickness, and metabolic alkalosis.

Question 8

What are the therapeutic uses of osmotic diuretics?

Answer 8

Osmotic diuretics are used in acute or impending renal failure and for the reduction of intraocular or intracranial pressure.

Question 9

What are the main functions of tubular reabsorption in the proximal tubule?

Answer 9

The proximal tubule reabsorbs 2/3 of water and NaCl, bicarbonate, glucose, amino acids, and organic solutes.

Question 10

What happens in the descending limb of the Loop of Henle?

Answer 10

The descending limb is relatively impermeable to sodium and chloride but permeable to water, allowing water to diffuse out.

Question 11

What occurs in the thick ascending limb of the Loop of Henle?

Answer 11

The thick ascending limb reabsorbs 25–35% of sodium and chloride and is impermeable to water.

Question 12

What occurs in the distal tubule?

Answer 12

The distal tubule reabsorbs 10% of sodium chloride and remains impermeable to water.

Question 13

What occurs in the collecting tubule?

Answer 13

The collecting tubule reabsorbs only ~3% of sodium chloride and is the primary site of potassium secretion (stimulated by aldosterone).

Question 14

What are the characteristics of tubular secretion/reabsorption of organic acids and bases?

Answer 14

This process occurs mainly in the proximal tubule and is characterized as an active process that is saturable and may involve competitive inhibition.

Question 15

What is the mechanism of action of osmotic diuretics?

Answer 15

Osmotic diuretics act based on osmotic pressure created in solution, decreasing sodium reabsorption in the proximal tubule and increasing medullary blood flow in the descending loop of Henle and collecting duct.

Question 16

What are the side effects of osmotic diuretics?

Answer 16

Side effects include rapid increase in plasma volume (may cause heart failure or pulmonary edema), hypernatremia, hyperkalemia, nausea, vomiting, and headache.

Question 17

What is the mechanism of action of carbonic anhydrase inhibitors?

Answer 17

Carbonic anhydrase inhibitors inhibit carbonic anhydrase in the proximal tubule, leading to increased bicarbonate excretion.

Question 18

What are the therapeutic uses of carbonic anhydrase inhibitors?

Answer 18

They are used to reduce intraocular pressure (glaucoma), treat metabolic alkalosis, alkalinize urine (e.g., cystinuria), and for epilepsy and altitude sickness.

Question 19

What are the side effects of carbonic anhydrase inhibitors?

Answer 19

Side effects include metabolic acidosis, drowsiness, fatigue, and paresthesias.

Question 20

What are loop diuretics known for?

Answer 20

Loop diuretics are the most potent class and may inhibit reabsorption of up to 25% of glomerular filtrate.

Question 21

What is the mechanism of action of loop diuretics?

Answer 21

They are actively secreted into the proximal tubule and inhibit Na⁺/K⁺/2Cl⁻ cotransport in the thick ascending limb of the Loop of Henle.

Question 22

What are the side effects of loop diuretics?

Answer 22

Side effects include hypokalemia, hyperuricemia, metabolic alkalosis, hyponatremia, and ototoxicity.

Question 23

What is the mechanism of action of thiazide diuretics?

Answer 23

Thiazide diuretics inhibit Na⁺/Cl⁻ cotransport in the distal convoluted tubule and may possess weak carbonic anhydrase inhibition.

Question 24

What are the therapeutic uses of thiazide diuretics?

Answer 24

Thiazides are used for hypertension, CHF, nephrolithiasis (renal calculi), nephrogenic diabetes insipidus, and osteoporosis.

Question 25

What are the side effects of thiazide diuretics?

Answer 25

Side effects include hypokalemia, hyponatremia, hypochloremic alkalosis, hypomagnesemia, hyperuricemia, hypercalcemia, hyperglycemia, and hyperlipidemia.

Question 26

What are potassium-sparing diuretics?

Answer 26

Potassium-sparing diuretics are weak diuretics commonly used in combination with thiazides or loop diuretics to prevent potassium loss.

Question 27

What is the mechanism of action of potassium-sparing diuretics?

Answer 27

They interfere with sodium reabsorption and potassium secretion in the collecting tubule, with spironolactone acting as an aldosterone antagonist.

Question 28

What are the side effects of potassium-sparing diuretics?

Answer 28

Side effects include hyperkalemia, gynecomastia, hirsutism, and menstrual irregularities (specific to spironolactone).

Question 29

What are key drug interactions with diuretics?

Answer 29

1. Thiazides + Beta Blockers: Risk of hyperglycemia, hyperuricemia, hyperlipidemia. 2. Thiazides/Loops + Digoxin: Hypokalemia increases risk of digitalis toxicity. 3. ACE Inhibitors + Potassium-Sparing Diuretics: Risk of hyperkalemia. 4. Aminoglycosides + Loop Diuretics: Increased risk of ototoxicity and nephrotoxicity. 5. Adrenal Steroids + Thiazides/Loops: Additive hypokalemia.

Question 30

What is a clinical consideration regarding diuretics?

Answer 30

Abrupt withdrawal of diuretics may lead to paradoxical edema due to elevated plasma renin and aldosterone.