7 - Diuretics

Question 1

acetazolamide - mech

Answer 1

inhibit carbonic anhydrase in PCT
inc NaBicarb diuresis
can cause hyperchloremic metab acidosis

Question 2

clinical uses of acetazolamide

Answer 2

glaucoma
urinary alkalinization (inc solubility of uric acid and cysteine)
metab alkalosis (diuretic induced)
acute mountain sickness

Question 3

acetazolamide AEs

Answer 3

hyperchloremic metab acidosis

hypokalemia

Question 4

how do most diuretics cause renal K wasting?

Answer 4

inc distal Na delivery drives K secretion (Na-K exchangers that aldosterone works on)

Question 5

how do osmotic diuretics work?

Answer 5

prevent water reabs in PCT and dLoH
oppose ADH action in CD
inc urine flow rate > dec contact time btwn fluid and tubular epithelium > reduce Na reabs > diuresis

Question 6

uses of osmotic diuretics (eg mannitol)

Answer 6

cerebral edema
acute congestive glaucoma
prevent oliguric phase in AKI (ex hemolysis, rhabdomyolysis)

Question 7

osmotic diuretic AEs

Answer 7

EC volume expansion + hyponatremia

dehydration + hypernatremia

Question 8

loop diuretic mechanism

Answer 8

inhibit Na/K/2Cl transporter in TAL of Loop
very potent - induces NaCl diuresis
inc Mg and Ca excretion b/c dec luminal positive potential
K wasting
induce renal PG synth > inc RBF and vasodilation

Question 9

uses of loop diuretics

Answer 9

pulm edema
edematous conditions (heart failure, cirrhosis, nephrotic syndrome)
HTN - refractory, assoc w/ renal insuff or HF, HTN emergency
hypercalcemia and hyperkalemia
SIADH

Question 10

how does furosemide work to counter SIADH?

Answer 10

block Na reabs in loop of henle >
abolish hyperosmolarity of medulla >
hinder Na reabs due to ADH in distal nephron

Question 11

loop diuretics AEs

Answer 11

hypokalemic metab alkalosis
hypomagnesemia
hyperuricemia
ototoxicity (dose related)

Question 12

thiazide diuretics mechanism

Answer 12

block Na/Cl cotransporter in DCT
induce NaCl diuresis
inc Ca reabsorption
renal K wasting

Question 13

uses of thiazides

Answer 13

HTN
heart failure
renal stones due to idiopathic hypercalciuria
nephrogenic DI

Question 14

how do thiazides work in nephrogenic DI?

Answer 14

thiazide induced Na loss stimulates Na reabs in PCT > dec urine formation over time

Question 15

thiazides AEs

Answer 15

hypokalemic metab acidosis
hyperuricemia
hyponatremia
hyperglycemia
hyperlipidemia

Question 16

mechanisms of both types of K sparing diuretics

Answer 16

spironolactone/eplerenone - direct antagonism of MR receptors (aldosterone)

amiloride/triamterene - inhibition of Na entry through ion channels in luminal membrane

both increase urine NaCl excretion
can cause hyperkalemia / metabolic acidosis

Question 17

K sparing diuretic use

Answer 17

primary and secondary hyperaldosteronism
heart failure
cirrhosis

Question 18

K sparing diuretic AEs

Answer 18

hyperkalemia
hyperchloremic metab acidosis (like type IV RTA)
gynecomastia (specifically spironolactone)

Question 19

approaches to diuretic resistance

Answer 19

make sure they are following salt restriction + med intake
discontinue NSAIDs
adjust dose of diuretic if renal impairment - protein bound diuretic gets wasted in albuminuria
switch to IV admin if absorption is a concern
continuous IV infusion for loop diuretic to avoid postdiuretic salt retention
combine loop diuretics w/ other diuretics (preferably thiazide)