Diuretics

Question 1

Indications for diueretics

Answer 1

Tx of HTN, mobilization of edematous fluid from HF, cirrhosis, kidney disease. Also maintain urine flow so used to prevent renal failure

Question 2

4 functional regions of the kidney

Answer 2

Glomerulus, proximal convoluted tubule, loop of Henle, distal convoluted tubule (plus collecting duct)

Question 3

Three basic functions kidney

Answer 3

Cleaning and maintaining ECF, pH, excretion of wastes

Question 4

Fluid through kidneys

Answer 4

125mL/minute or 180L/day (Volume of ECF is 12.5L so entire amount is filtered every 100 minutes)

Question 5

Reabsorption of solutes is what kind of transport

Answer 5

Active

Question 6

PCT

Answer 6

65% sodium and chloride reabsorbed at proximal convoluted tubule
Almost all bicarb and k+ here

Question 7

Descending limb, loop of henle

Answer 7

Freely permeable to water. Water is drawn into interstitial space, and increases tonicity from 300mOsm/L to 1200mOsm/L

Question 8

Ascending limb loop of Henle

Answer 8

In thick segment 20% sodium and chloride is reabosrbed. Not permeable to water so returns to 300mOsM/L

Question 9

Early distal convoluted tubule

Answer 9

10% sodium and chloride reabsorbed here. Water follows passively

Question 10

Late distal and collecting duct

Answer 10

Exchange of sodium for potassium under influence of aldosterone.
Final concentration of urine regulated by ADH

Question 11

Aldosterone sodium/potassium exchange

Answer 11

Stimulates reabsorption of Na+ from DCT, and causes K+ to be secreted.
Aldosterone stimulates cells of distal nephron to synthesize more pumps which retain sodium and boot potassium

Question 12

4 classes of diuretics

Answer 12

Loop (high-ceiling) eg lasix
Thiazide
Osmotic
K+ sparing (divided into aldosterone antagonists and nonaldosterone antagonists)

Question 13

Loop diuretics

Answer 13

Site of action is loop of henle (hence the name)

Furosemide

Question 14

Furosemide

Answer 14

Thick segment of ascending loop, blocks reabsorption of sodium and chloride. This prevents passive reabsorption of water

Question 15

Pharmacokinetics of furosemide

Answer 15

Oral diuresis begins in 60 minutes persists for 8 hours
IV begins in 5 and lasts for two hours
CAN produce renal flow with a low GFR (good for pts with severe renal impairment)
No benefit in adding a second loop, but benefits in adding a thiazide

Question 16

Adverse effects of furosemide

Answer 16

Hyponatremia, hypochloremia, dehydration.
Dehydration can promote thrombosis and embolism.
Hypokalemia
Hypotension from both fluid loss and relaxation of smooth muscle
Ototoxicity - hearing impairment. Rare and transient with lasix
Hyperglycemia from inhibition of insulin
Hyperuricemia (gout)
Dangerous in pregnancy
Reduced HDL and raises LDL (still drop risk of coronary mortality by 25%)
Hypomagnesia and hypocalcemia

Question 17

NSAIDS and lasix

Answer 17

NSAIDS reduce effectiveness as lasix uses renal flow secondary to prostaglandins to work

Question 18

Lasix dose

Answer 18

20-80mg a day starting. Max 600mg

Question 19

Thiazides

Answer 19

Also increase renal excretion of NaCl, K+ and water
Principal difference is max diuresis is significantly lower
Are not effective with decreased renal flow like loops are

Question 20

Thiazide MOA

Answer 20

Early distal convoluted tubule. 10% NaCl reabsorbed here so lower ceiling than loops.
GFR needs to be more than 20mL/min to work
Works in 2 hours peaks at 4-6, persist for 12

Question 21

Thiazide for diabetes insipidus

Answer 21

Increased urine output in DI, for an unknown reason thiazides reduce this.
These drugs promote renal reabsorption of calcium (loops excrete it) and can be used for osteoporosis

Question 22

Sides of thiazides

Answer 22

HypoNaCl and dehydation
Hypokalemia
Hyperglycemia
Hyperuricemia
Increase LDL and total cholesterol
CAN be used with other ototoxic drugs unlike loops

Question 23

Diuretics and digoxin

Answer 23

Hypokalemia and dig is dangerous so loops and thiazides are badness

Question 24

K+ sparing diuretics

Answer 24

Modest effect on urine output

Question 25

Spironolactone

Answer 25

Blocks aldosterone in distal nephron (aldosterone increases Na reabsorption decreases K+)
Blocks NEW proteins but does not stop existing so takes up to 48 hours to work

Question 26

Adverse effects of K+ spironolactone

Answer 26

Hyperkalemia

Steroid derivative and can cause gyno, mesntral problems, impotence, hirsutism and deepening of voice

Question 27

Which are the osmotic diuretics

Answer 27

Mannitol, glycerin and isosorbide

Question 28

MOA mannitol

Answer 28

Six-carbon sugar
Freely filtered at glomerulus 
Undergoes minimal tubular reabsorption
Minimal metabolism
Has no direct effects on biochemistry of cells

Question 29

Mannitol pharmacokinetics

Answer 29

Can’t be taken orally, won’t be absorbed. Diuresis begins 30-60 minutes after admin and lasts 6-8 hours

Question 30

Mannitol uses

Answer 30

Prevent renal failure. Since it is not reabsorbed it makes water keep running through in severely dehydrated patients
Reduction of ICP and intraocular pressure

Question 31

Adverse mannitol effects

Answer 31

Edema as it leaves vascular system at capillary beds (except in the brain)
Headache, N/V, fluid/lyte imbalances