Diuretics

Question 1

what % of sodium reabsorbed in each nephron segments?

Answer 1

Proximal - 60%
LOH - 15-25%
Distal tubule 5-10%
CD 4%

Question 2

how do diuretics act in pts w/ chronic renal disease?

Answer 2

CKD: decreased renal blood flo wand anionic metabolites –> reduce diuretic renal excretion rate
nephrotic syndrome: hypoalbuminemia increases Vd and decreases renal excretion rate

Question 3

why does diuretic resistance occur? (3)

Answer 3

1. decreased renal clearance
2. sodium retention in response to increased ATII, catecholamines, aldosterone, and resistance to ANP
3. DCT hypertrophy

Question 4

options for management of diuretic resistance

Answer 4

increase dose
use loop diuretic and thiazide diuretic in combo
restrict fluid and salt intake
add aldosterone antagonist
avoid vasodilator that impairs renal perfusion

Question 5

how to treat nephrogenic DI?

Answer 5

thiazides and amiloride

Question 6

options for modifying drug dosage in pts w/ renal impairment

Answer 6

select drug cleared by non renal mechanisms
OR
reduce infusion rate, maintain w/ dose interval according to fraction of renal total clearance

Question 7

which drug for Liddle’s

Answer 7

amiloride

Question 8

HCT

Answer 8

inhibits NaCL cotransporter in DT

increases K excretion, enhances Ca reabsorption

Question 9

Furosemide

Answer 9

Blocks Na-K-2Cl symporter in TAL –> blocks urinary diluting and conc capacity
increases distal Na delivery –> more K excretion
increases Ca and Mg excretion

Question 10

tox from furosemide

Answer 10

ototoxicity
hyperuricemia
hypersensitivity

Question 11

spironolactone

Answer 11

K-sparing diuretic: competitive antagonism w/ aldosterone

blocks MR-induced increase in ENaC expression and membrane insertion

Question 12

SE of spironolactone

Answer 12

hyperkalemia

endocrine abnormalities: gynecomastia, impotence

Question 13

mannitol

Answer 13

osmotic diuretic - decreases water resorption

enhanced Na and K excretion through solute drag

Question 14

indications for mannitol

Answer 14

glaucoma
cerebral edema
maybe AKI
(times when you need to rapidly shrink intracellular volume)

Question 15

acetazolamide

Answer 15

carbonic anhydrase inhibitor: blocks bicarb resorption in PT; increases urinary excretion of Na and bicarb
causes metabolic acidosis
less H+ available in distal tubule –> more K+ secretion

Question 16

toxicities from acetazolamide

Answer 16

hypokalemia
calcium stones b/c alkaline urine
hypersensitivity rxns to sulfa

Question 17

acetazolamide indications

Answer 17

mountain sickness
glaucoma
metabolic alkalosis

Question 18

amiloride

Answer 18

ENaC channel blocker

Question 19

indications for amiloride

Answer 19

diuretic in hypokalemia
Liddle’s disease
in combo w/ thiazides to prevent Li-induced nephrogenic DI

Question 20

eplerenone

Answer 20

K-sparing diuretic - like spironolactone but more selective for MR receptors (over androgen and progesterone)

Question 21

DDAVP/desmopressin

Answer 21

long-acting analogue of vasopressin w/ high selectivity for V2 receptors over V1
for tx central DI

Question 22

which diuretic can cause hyperkalemia?

Answer 22

spironolactone

Question 23

calcium-sparing diuretics

Answer 23

thiazide