Diuretics

Question 1

Your patient is starting on a potassium-sparing diuretic and is worried about side effects. What do you tell him?


Answer 1

Side effects include hyperkalemia (leading to arrhythmias) and endocrine effects with spironolactone (gynecomastia and antiandrogen effects)

Question 2

____ (Loop/Thiazide) diuretics increase calcium excretion; ____ (loop/thiazide) diuretics decreases it.


Answer 2

Loop; thiazide


Question 3

What mechanism underlies volume contraction alkalosis?


Answer 3

Volume contraction increases angiotensin II activity, increasing proximal tubule H+/Na+ exchange and HCO3- reabsorption


Question 4

Where does parathyroid hormone increase calcium reabsorption in the nephron?


Answer 4

Distal convoluted tubule


Question 5

A patient of yours with a history of gout and diabetes wants to start hydrochlorothiazide for hypertension. You refuse. Why?


Answer 5

Hydrochlorothiazide increases levels of both uric acid and glucose, which may worsen the patient’s gout and diabetes, respectively


Question 6

Fill in the blanks (thiazides/K+-sparing diuretics/loop diuretics/acetazolamide): ___ and ___ raise blood pH; ___ and ___ lower blood pH.


Answer 6

Loop diuretics and thiazides raise blood pH; acetazolamide and K+-sparing diuretics lower blood pH


Question 7

What are three (general) clinical uses for loop diuretics?


Answer 7

To treat edematous states (congestive heart failure, cirrhosis, nephrotic syndrome, pulmonary edema), hypertension, and hypercalcemia


Question 8

A patient starts a potassium-sparing diuretic. What are the main electrolytes absorbed and secreted at the site where this drug acts?


Answer 8

Potassium-sparing diuretics act on the collecting tubule, where NaCl (reabsorbed), K+ (secreted), and H+ (secreted) are exchanged


Question 9

A patient taking torsemide is noted to have dilated renal afferent arterioles. This effect is blocked by NSAIDs. What is happening?


Answer 9

Torsemide, a loop diuretic, dilates the afferent arterioles by stimulating prostaglandin E (PGE) release, an effect inhibited by NSAIDs


Question 10

A patient starts taking acetazolamide for mild altitude sickness. What is the mechanism of action of this drug?


Answer 10

It acts as a carbonic anhydrase inhibitor, causing self-limited sodium bicarbonate diuresis and a reduction in total-body bicarbonate stores


Question 11

A patient takes mannitol. On which segments of the nephron does an osmotic agent such as mannitol exert its diuretic effects?


Answer 11

Proximal straight tubule and the thin descending loop of Henle


Question 12

A patient takes a diuretic for increased intracranial pressure. What is the drug and its mechanism of action?


Answer 12

Mannitol, an osmotic diuretic, which increases tubular fluid osmolarity and therefore urine flow rate (also acts on intraocular pressure)


Question 13

A patient of yours starts chlorthalidone for hypertension and notes fewer kidney stone attacks. Why might this be happening?


Answer 13

Hydrochlorothiazide increases DCT reabsorption of calcium, which reduces the likelihood of calcium-containing stones in the urine

Question 14

In a patient on diuretics, labs show a high urine sodium and a low serum sodium. Can you pinpoint which diuretic(s) may be responsible?


Answer 14

Except for acetazolamide, no (all diuretics can cause this effect, so this is a nonspecific finding)


Question 15

A patient on a loop diuretic is noted to have elevated calcium in his urine. Is the loop diuretic responsible?


Answer 15

Yes; loop diuretics decrease paracellular Ca2+ reabsorption, leading to increased urinary Ca2+ levels and hypocalcemia


Question 16

What is the mechanism by which potassium-sparing diuretics cause acidemia?


Answer 16

Hyperkalemia leads to potassium entering all cells via the H+/K+ exchanger in exchange for H+ exiting cells


Question 17

A patient with SIADH is given ADH antagonists for severe hyponatremia. Where do these act, and what do they block from being reabsorbed?


Answer 17

ADH antagonists act on the collecting duct, blocking the ADH-mediated reuptake of water


Question 18

In the nephron, a site where only water is reabsorbed (without other electrolytes) is at the ____.


Answer 18

Thin descending limb of the loop of Henle


Question 19

By what mechanism involving all cells does potassium loss lead to alkalemia?


Answer 19

K+ exits all cells (to maintain a normal serum level) in exchange for H+ entering cells (causing the alkalemia)


Question 20

A man receives loop diuretics for a heart failure flare. How permeable to water is the site where they act? Are electrolytes absorbed there?


Answer 20

They act on the thick ascending loop of Henle, which is impermeable to water; yes (Mg2+, Ca2+, and Cl- are absorbed there)


Question 21

A patient begins taking a second diuretic to offset the effect of furosemide. What part of the nephron does this second diuretic act upon?


Answer 21

The cortical collecting tubule (this is likely a potassium-sparing diuretic)


Question 22

What is the mechanism of action of loop diuretics?


Answer 22

They block Na+/K+/Cl- thick ascending limb cotransporters, abolish medullary hypertonicity, and prevent urine concentration


Question 23

A patient with a sulfa allergy needs urgent loop diuretic diuresis due to heart failure. What medication can you offer him?


Answer 23

Ethacrynic acid (it is a phenoxyacetic acid derivative, not a sulfonamide)

Question 24

What are the mechanisms of action of spironolactone and eplerenone? What about triamterene and amiloride?


Answer 24

Spironolactone and eplerenone competitively antagonize the aldosterone receptor; triamterene and amiloride block luminal sodium channels


Question 25

A patient starts a thiazide diuretic for hypertension. This acts at the same site as which prominent hormone?


Answer 25

Thiazide diuretics act on the distal convoluted tubule, where PTH acts to moderate Ca2+ absorption

Question 26

A patient on a carbonic anhydrase inhibitor develops acidemia. What is the likely cause?


Answer 26

Acetazolamide causes the kidney to excrete more HCO3-, decreasing the body's pH and leading to acidemia


Question 27

Calcium excretion is increased by ____ (loop diuretics/thiazides) and decreased by ____ (loop diuretics/thiazides).


Answer 27

Loop diuretics (decreased paracellular reabsorption ); thiazides (enhanced paracellular reabsorption in proximal tubule and loop of Henle)


Question 28

Name some clinical indications for acetazolamide.


Answer 28

Glaucoma, urinary alkalinization, metabolic alkalosis, altitude sickness, pseudotumor cerebri

Question 29

A patient with anuria presents with heart failure. Is it safe to give this patient an osmotic diuretic?


Answer 29

No (osmotic diuretics such as mannitol are contraindicated in patients with anuria and/or heart failure)

Question 30

What is the effect of the loop diuretic furosemide on calcium handling in the kidney nephron?


Answer 30

Furosemide increases calcium excretion (Loops Lose calcium)


Question 31

Potassium and hydrogen secretion occurs at the ____ (cortical/medullary/both cortical and medullary) collecting tubule of the nephron.


Answer 31

Both cortical and medullary


Question 32

Name at least two toxicities associated with acetazolamide.


Answer 32

Hyperchloremic metabolic acidosis (ACIDazolamide causes ACIDosis), paresthesias, ammonia toxicity, sulfa allergic reactions


Question 33

Name some clinical uses of thiazide diuretics.


Answer 33

To treat hypertension, congestive heart failure, idiopathic hypercalciuria, nephrogenic diabetes insipidus


Question 34

Serum levels of which substances are increased as a result of the effects of thiazide diuretics?


Answer 34

Glucose (hyperGlycemia), lipids (hyperLipidemia), uric acid (hyperUricemia), and calcium (hyperCalcemia) (hyperGLUC)


Question 35

Both calcium and magnesium are reabsorbed primarily in the renal ____ (cortex/outer medulla/inner medulla).


Answer 35

Cortex


Question 36

Name some clinical uses of potassium-sparing diuretics.


Answer 36

To treat hyperaldosteronism, potassium depletion, congestive heart failure


Question 37

A patient takes acetazolamide for altitude sickness. What are the main electrolytes absorbed at the site where this drug acts?


Answer 37

It acts on the proximal convoluted tubule, where NaCl and NaHCO3-


Question 38

How does a low potassium state lead to alkalemia and a paradoxical aciduria?


Answer 38

H+ rather than K+ is exchanged for Na+ at the cortical collecting tubule

Question 39

Ethacrynic acid (a phenoxyacetic acid derivative) is an alternative to ____ for patients who suffer from \_\_\_\_. Name one toxicity.


Answer 39

Loop diuretics (furosemide, bumetanide, torsemide); sulfa allergies; hyperuricemia (never use ethacrynic acid to treat gout)


Question 40

Name at least four toxicities associated with using loop diuretics.


Answer 40

Ototoxicity, Hypokalemia, Dehydration, Allergy (sulfa), Nephritis (interstitial), Gout (OH DANG!)


Question 41

What acid-base abnormality is associated with thiazide diuretic use?


Answer 41

Hypokalemic metabolic alkalosis


Question 42

A patient is noted to have low serum potassium and high levels of potassium in the urine. Could a diuretic be responsible?


Answer 42

Yes (all except the potassium-sparing diuretics can cause these findings)