2B : DIURETICS - OSMOTIC DIURETICS

Question 1

OSMOTIC DIURETICS
DRUGS

Answer 1

glycerin, isosorbide, mannitol , urea

Question 2

Prototype :

Answer 2

Mannitol

Question 3

SITE OF ACTION

Answer 3

LoH & PT

Question 4

MOA

Answer 4

decreases H2O reabsorption by
increasing osmotic pressure of tubular fluid

Question 5

Osmolality retains

Answer 5

water in tubule

Question 6

Effects of MANNITOL

Answer 6

1. increased urine volume
2. increased urinary excretion of most solutes & nearly all electrolytes
3. greatly increased Na+ excretion (accelerated rate of urine flow through tubule; Na+ transporters cannot handle volume rapidly
   enough)
4. reduces brain volume & ICP
   by osmotically extracting H2O from tissues into the blood
   (similar effect in eye)

Question 7

Therapeutic uses of
Osmotic Diuretics

Answer 7

1. Increasing urine volume in oliguric ATN
2. Dialysis Disequilibrium Syndrome
3. Extraction of H2O from the brain
4. Reduction of Intraocular Pressure

Question 8

Mannitol
may provide renal protection by :

Answer 8

1. removing obstructing tubular casts
2. diluting nephrotoxic substances
3. reducing swelling of tubular elements via osmotic extraction of H2O

Question 9

true or false

Pts who respond will recover more rapidly & require less dialysis

Answer 9

true

Question 10

mannitol
& urea role in dialysis disequilibrium syndrome

Answer 10

increase ECF osmolality ,
causes water to shift back to ECF

Question 11

Pharmacokinetics of mannitol

Answer 11

poorly absorbed from the GI tract when administered orally causing an osmotic diarrhea

Question 12

must
be given for _____ systemic
effects

Answer 12

parenterally

Question 13

true or false

osmotic diuretics are excreted by glomerular filtration within 30-60 mins without any important reabsorption, secretion or metabolism

Answer 13

true

Question 14

MANNITOL: Effects on
Renal Hemodynamics

Answer 14

1. increases Renal Blood Flow
   by various mechanisms
2. dilates afferent arteriole

Question 15

how can mannito; increase RBF

Answer 15

1. expands ECF volume
2. decreases blood viscosity
3. inhibits renin release

all effects of extracting water from intracellular compartments

Question 16

Absorption and Elimination

Mannitol

Answer 16

• parenteral
• oral administration causes osmotic diarrhea
• T1/2 (h) 0.25 to 1.7 in renal failure
• min metabolism, excreted by
  glomerular filtration within
  30 60min, no important tubular reabsorption or secretion

Question 17

Absorption and Elimination
Glycerin &
Isosorbide

Answer 17

orally active, elimination ~80%
metabolism

Question 18

Toxicity & Adverse Effects

common AE :

Answer 18

• headache, nausea, vomiting
• hyponatremia from extraction of H2O
• hypernatremia & dehydration resulting from loss of H2O in excess of electrolytes
• hyperkalemia from increased intracellular K+ concentration
• frank pulmonary edema
  in pts with HF or pulmonary
  congestion - resulting from ECF volume expansion

Question 19

mannitol can cause Extracellular
volume expansion, what is the effect

Answer 19

Mannitol is distributed to extracellular space extracts water
from cells, leading to an expansion of extracellular volume hyponatremia before mannitol produces a diuresis

This can complicate heart
failure produce pulmonary edema

Question 20

s/e Dehydration,
hyperkalemia hypernatremia

Answer 20

These side effects can result from use of mannitol without adequate water replacement

Question 21

s/e Headache,
nausea vomiting

Answer 21

are commonly
observed

Question 22

can cause thrombosis/pain from extravasation

Answer 22

urea

Question 23

true or false

do not give to pts with impaired liver function because of risk of elevation of blood ammonia levels

Answer 23

true

Question 24

glycerin
is metabolized can cause

Answer 24

hyperglycemia

Question 25

mannitol
& urea

Answer 25

Contraindicated in active cranial bleeding

Question 26

osmotic diuretics ContraIndicated in

Answer 26

anuric pts who are unresponsive
to test doses of ODs