Diuretics

Question 1

What are diuretics?

Answer 1

Diuretics increase excretion of electrolytes and water.

Question 2

What are the indications for diuretic use?

Answer 2

• Inappropriate salt and water retention: CHF, renal or liver disease
• Oliguric states
• Chronic lung disease
• Electrolyte disturbances

Question 3

Why is understanding kidney function important for diuretic use?

Answer 3

Understanding diuretic use requires knowledge of kidney function.

Question 4

What is the major active solute in extracellular fluid (ECF)?

Answer 4

NaCl

Question 5

How is extracellular fluid volume (EFV) regulated?

Answer 5

• Sodium intake vs. urinary sodium excretion
• Cardiac output and BP
• Short-term: Glomerular infusion rate
• Long-term: Aldosterone

Question 6

What does glomerular filtration rate (GFR) measure?

Answer 6

The amount of filtrate formed in glomerulus per minute.

Question 7

How is GFR commonly measured?

Answer 7

By creatinine clearance.

Question 8

What maintains renal blood flow?

Answer 8

Vasoconstriction/vasodilation of afferent/efferent arterioles.

Question 9

What regulates renal blood flow?

Answer 9

• Renin-angiotensin-aldosterone system (RAAS)
• ADH
• Atrial and beta-natriuretic factors

Question 10

What triggers the activation of RAAS and ADH?

Answer 10

Decreased perfusion.

Question 11

What is the goal of the renin-angiotensin-aldosterone-ADH system?

Answer 11

Maintain renal perfusion and vital organ blood flow.

Question 12

What does renin convert angiotensinogen into?

Answer 12

Angiotensin I.

Question 13

What is the role of ACE in the renin-angiotensin-aldosterone system?

Answer 13

Converts angiotensin I into angiotensin II, a potent vasoconstrictor.

Question 14

What effects does aldosterone have?

Answer 14

• Increases Na, Cl, and water reabsorption
• Increases K+ and H+ excretion

Question 15

What does ADH do?

Answer 15

Increases water reabsorption in collecting ducts.

Question 16

What does ANP stand for and when is it secreted?

Answer 16

Atrial Natriuretic Peptide; secreted by atria due to increased intravascular volume.

Question 17

What are the effects of natriuretic peptides?

Answer 17

• Decrease renin and aldosterone release
• Vasodilation
• Decrease BP
• Increase diuresis

Question 18

What are the four main functions of the renal tubules?

Answer 18

• Filtration
• Reabsorption
• Secretion
• Excretion

Question 19

What percentage of potassium is reabsorbed in the proximal tubule?

Answer 19

65%

Question 20

What regulates potassium levels in the kidneys?

Answer 20

K+ levels, acid-base balance, aldosterone.

Question 21

What is the basic principle of diuretic action?

Answer 21

Block reabsorption of Na and water.

Question 22

What is the effect of early action of diuretics?

Answer 22

Greater effect.

Question 23

What is a key consideration for neonatal diuretic use?

Answer 23

Renal tubule immaturity leads to decreased response to diuretics.

Question 24

What is an example of a carbonic anhydrase inhibitor?

Answer 24

Acetazolamide (Diamox).

Question 25

What is the effectiveness of carbonic anhydrase inhibitors?

Answer 25

Weak (5% Na/water excretion).

Question 26

What is the mechanism of action for osmotic diuretics?

Answer 26

Not reabsorbed, increases tubular osmolality, draws water into tubules.

Question 27

What is an example of a loop diuretic?

Answer 27

Furosemide (Lasix).

Question 28

What is the mechanism of action of loop diuretics?

Answer 28

Blocks Na, K, Cl reabsorption in ascending loop of Henle.

Question 29

What are the adverse effects of loop diuretics?

Answer 29

* Ototoxicity * Electrolyte loss * Volume depletion * Metabolic alkalosis * Risk of nephrocalcinosis, rickets

Question 30

What is an example of a thiazide diuretic?

Answer 30

Hydrochlorothiazide.

Question 31

What is the mechanism of distal diuretics (thiazides)?

Answer 31

Inhibit NaCl reabsorption in distal tubule.

Question 32

What are the common adverse effects of thiazide diuretics?

Answer 32

* Digoxin toxicity risk * Hyperglycemia * GI symptoms * Thrombocytopenia

Question 33

What is an example of a potassium-sparing diuretic?

Answer 33

Spironolactone (Aldactone).

Question 34

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

Answer 34

Blocks Na reabsorption and acts as an aldosterone antagonist.

Question 35

What is the pharmacokinetics of spironolactone?

Answer 35

Oral bioavailability 90%, onset 2–3 days.