Chapter 7 - Drug Clearance

Question 1

“clearance” is a theoretical concept that describes eliminating drug from the body without doing what???

Answer 1

WITHOUT IDENTIFYING THE SPECIFIC MECHANISM OF THE PROCESS – only care about how much is removed

Question 2

TOTAL BODY CLEARANCE is a combination of what 2 things

Answer 2

renal clearance and non-renal clearance (but the non-renal clearance is usually negligible!!

Question 3

name 4 factors that affect the clearance of a drug

Answer 3

age
sex
kidney disease
cardiac disease

Question 4

how does age affect drug clearance

Answer 4

after the age of 70, clearance decreases

Question 5

**how does sec affect drug clearance

Answer 5

clearance is 10% lower in females than in males

Question 6

if a drug undergoes glomerular filtration ONLY, what will the clearance be

Answer 6

130mL/min

Question 7

true or false

renal clearance changes depending on the drug

Answer 7

FALSE - same for every drug, just different depending on each patient’s renal function

Question 8

2 methods of measuring renal clearance

Answer 8

-from the elimination rate constant on the plasma profile

-from the urinary excretion rate

Question 9

true or false

renal clearance is NOT AFFECTED by drugs and their concentration

Answer 9

TRUE

renal clearance of kidney function of a subject is a CONSTANT VALUE and is not affected by varying drugs

Question 10

true or false

just by looking at the clearance, it’s not possible to tell what the mechanism of excretion is

Answer 10

true

Question 11

a drug ONLY undergoes glomerular filtration and some of it is reabsorbed

what is the range that the clearance can be

Answer 11

0-129mL/min

Question 12

a drug undergoes both passive and active secretion. no reabsorption

what can the clearance range be

Answer 12

130-650mL/min

Question 13

the clearance of a drug is CONSTANT over time

can we assume it is cleared through passive mechanism (glomerular filtration) only

Answer 13

yes

Question 14

true or false

the graph of pure glomerular filtration is linear

Answer 14

TRUE

rate depends on plasma concentration - 1st order kinetics

Question 15

the clearance value is LESS THAN the glomerular filtration rate (130mL/min)

what can be assumed?

Answer 15

the drug is reabsorbed

Question 16

what is the normal value for TOTAL CLEARANCE

Answer 16

650mL/min

Question 17

formula for half life of drugs solely eliminated through the kidneys

Answer 17

t1/2 = (0.693)(Vd)/Cl

Question 18

true or false

as the Vd increases, the t1/2 decreases

Answer 18

FALSE

t1/2 increases as the Vd increases

Question 19

true or false

if the volume of distribution is large, we may need to decrease the dose

Answer 19

false - increase. to keep the plasma concentration high

Question 20

if clearance is high, half life can be expected to be….

Answer 20

short

Question 21

true or false

as K decreases, Cl increases

Answer 21

FALSE - ANYTHING CAN HAPPEN TO Cl – we dont know

K does not affect Cl or V — Cl and V affect K

Question 22

true or false

as K decreases, V increases

Answer 22

FALSE - ANYTHING CAN HAPPEN TO V – we dont know

K does not affect Cl or X

Cl and V affect K

Question 23

define creatinine clearance

Answer 23

the rate of excretion of creatinine by the kidneys

Question 24

how does calculating the creatinine clearance save time

Answer 24

dont have to inject the patient with mannitol and do the whole experiment

Question 25

by what mechanism is creatinine excreted

Answer 25

mostly through glomerular filtration however, a VERY SMALL amount is actively secreted - therefore the GFR values tend to be a tiny bit higher than if we had measured through inulin clearance

Question 26

serum creatinine concentration of 2 represents a ____% kidney function what about a serum creatinine concentration of 4?

Answer 26

50% 4 SCr - 25% renal function

Question 27

name 3 methods of finding the creatinine clearance from the serum creatinine concentration

Answer 27

jelliffe method cockcroft gault method siersback-nielsen method

Question 28

which method of finding creatinine clearance is NOT FOR PATIENTS UNDER 20 YEARS OLD

Answer 28

jelliffe method

Question 29

true or false the siersback-nelsen method is used to calculate creatinine clearance in MATURE ADULTS ONLY

Answer 29

FALSE - this is the jelliffe method

Question 30

jelliffe method is usually only applicable up to what age

Answer 30

80 years old

Question 31

3 factors for determining CrCl through the jelliffe method

Answer 31

age serum creatinine conc gender (2 diff eqns)

Question 32

how does the cockcroft gault mehtod differ from the jelliffe method

Answer 32

accounts for age, serum creatinine, and gender, BUT ALSO INCLUDES WEIGHT AS A FACTOR

Question 33

The siersback-nelsen method is similar to the ____ method of finding creatinine clearance how?

Answer 33

cockcroft gault because it accounts for the same 4 factors - age, weight, gender, and serum creatinine - but in nomogram form

Question 34

95 year old patient has a CrCl of 42.75mL/min and SCr of 0/8mg/dl the amount of drug in urine was 10.32mL what do you have to say about her kidney function

Answer 34

just decreased efficacy due to aging. the serum creatinine is normal only 10.32mL of drug was in the urine probably due to reabsorption - NOT KIDNEY FAILURE

Question 35

true or false according to the cockcroft gault equation, women are expected to have 90% the kidney function of men naturally

Answer 35

FALSE - 85% jelliffe method estimates 90%

Question 36

75 year old patient has a CrCl of 60.75mL/min and an SCr of 0.8mg/dl there was found to be 60.75mL of drug in urine what do you have to say

Answer 36

this is not kidney failure - just deterioration due to age also this amount of drug in the urine indicates there was little-no reabsorption

Question 37

patient has a creatinine clearance of 48mL/min in what scenario would their clearance be exaclty 48mL/min

Answer 37

if the drug is ONLY REMOVED BY FILTRATION and no active secretion

Question 38

how many scales are there in the siersback-nielsen method of finding CrCl

Answer 38

5

Question 39

true or false infants have an estimated eGFR of 130mL/min

Answer 39

FALSE - THIS CONCEPT DOESNT APPLY TO NEWBORNS!!!!! there's is like 3mL/min

Question 40

what does "inulin clearance" refer to

Answer 40

the eGFR ONLY

Question 41

what does "PAH clearance" refer to

Answer 41

the total excretion - not only filtration!

Question 42

compare the water content of newborn vs adult

Answer 42

newborns have a higher water content

Question 43

the half life of PAH and inulin tends to be ______ in a newborn than in an adult

Answer 43

longer half life in a newborn

Question 44

2 methods of determining the creatinine clearance in PEDIATRICS what are the parameters used?

Answer 44

-Schwartz and associate -Traub and Johnson (another nomogram) both only use height and serum creatinine!! does NOT account for age or weight

Question 45

drugs taken orally get to the liver through the hepatic vein or artery

Answer 45

hepatic portal vein and hepatic artery leaves through vein

Question 46

2 methods of finding the hepatic clearance

Answer 46

-from total clearance-renal clearance -from hepatic extraction ratio

Question 47

drugs with a MW of _____ are destroyed by the liver and cannot be removed by the kidney

Answer 47

500 or more

Question 48

what is a very important factor that determines the extent of hepatic clearance

Answer 48

hepatic blood flow!

Question 49

what does an HER of 0.25 mean

Answer 49

25% of the drug was removed from the plasma by the liver

Question 50

the HER can range from ___ to ___. what do each of these values mean

Answer 50

0-1 if zero - NO drug was removed by the liver if 1 - ALL of the drug was removed by the liver