lecture 4 part 3 Flashcards

1
Q

name 3 body compartments into which the drug may be distributed

A

water
fat
bone

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2
Q

what drugs will get distributed to:

-total body water
-extracellular water
-blood

A

blood = heparin, strongly plasma bound and large molecules

total body water = small, water soluble molecules like ethanol

extracellular water = large, water soluble molecules like gentamicin

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3
Q

name drugs that will get distributed into the bone

A

certain ions like lead and fluoride

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4
Q

what things will get distributed into the fat

A

highly lipid soluble molecules

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5
Q

rank the following according to their Vd:

digoxin
acetaminophen
chloroquine

A

highest = chloroquine

digoxin

lowest = acetaminophen

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6
Q

true or false

clearance is additive

A

TRUE

function of elimination by ALL participating organs like the liver and kidney

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7
Q

name the 2 most important sites for drug elimination

A

liver and kidney

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8
Q

what are the units for clearance

A

mL/min

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9
Q

name the 2 main factors in renal excretion

A

-glomerular filtration
-passive tubular reabsorption

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10
Q

true or false

if a drug is strongly bound to protein, it will be filtered

A

FALSE – it will not be filtered and will go back to the blood

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11
Q

true or false

enhanced lipid solubility favors reabsorption

A

true

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12
Q

give an example of a drug that is completely reabsorbed

A

thiopental and all barbiturates

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13
Q

** name 4 things that affect renal tubular reabsorption rate

A

pH
pka compared to urine pH
weak acid or weak base
rate or renal tubular blood flow

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14
Q

what does it mean if a drug is “transferred to glomerular filtrate?”

A

it is secreted out of the body

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15
Q

true or false

when lipid soluble drugs are reabsorbed back into the body, the mechanism is through active transport

A

FALSE - passive

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16
Q

how does chronic ethanol use affect metabolism

A

it induces CYP2E1

therefore, the effect of ethanol won’t happen (or not as much) because it gets metabolized quickly

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17
Q

grapefruit juice

A

potent inhibitor of CYP3A4 (localized in intestinal wall mucosa)

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18
Q

genetic polymorphism of CYP2D6

A

5-10% of caucasians are poor metabolizers but only 1-2% for asian population

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19
Q

genetic polymorphism of CYP2C19

A

20% of asians are poor metabolizers and only 4% caucasian

20
Q

**** explain enterohepatic cycling and what xubstances go through it

A

glucuronide conjugates – hydrolyzed in GI back to the parent molecule.

parent molecule gets reabsorbed back into the body again and again – duration of action prolonged.

VITAMIN B12, VITAMIN D3, FOLIC ACID, ESTROGENS

21
Q

define half life

A

the time required to decrease the amount of drug in the bpdy by HALF during elimication

22
Q

explain what 1st order elimination is

A

a constant fraction of the drug dissapears from the body in an equal interval of time

23
Q

true or false

most elimination mechanism are through first order

A

true

24
Q

true or false

the concentration of drug in the plasma drops exponentially with time

A

true - 1st order kinetics

25
Q

explain zero order

A

elimination is constant and INDEPENDENT of drug concentration

very few drugs eliminated this way

26
Q

true or false

disease states do not affect half life

A

false – they do bc disease states affect clearance and VD

27
Q

** what is the average amount of half lives for a drug to be fully excreted

A

around 7

28
Q

one half life will reduce the drug by 50%

how much drug will be remaining after 2 half lives?

A

25%

29
Q

one half life will reduce the drug by 50%

how much drug will be remaining after 5 half lives?

A

3.12%

30
Q

one half life will reduce the drug conc in the body to 50%

how many half lives are needed to get to 12.5%?

A

3 half lives

31
Q

the half life is useful in estimating the time to reach……

A

steady state

32
Q

approximately ___ half lives are required to reach about ____% of a new steady state

A

4 half lives, 94%

33
Q

drug accumulation will be observed if…

A

the dosing interval is less than 4 half lives

34
Q

in the simplest case, drugs are directly related to…..

A

plasma concentration

35
Q

give reasons for delayed drug effects

A

the time required for the drug to distrubute from the plasma to the site of action

slow turnover of physiologic substances involved in producing the drug effect

warfarin inhibits vitamin k epoxidase in the liver. this forms a clotting complex with a long half life (14 hours)

36
Q

what is the “maintenance dose”

A

just enough drug is given in each dose to replace what has been eliminated since the preceding dose

37
Q

why might a loading dose be required?

A

to produce effective blood levels without delay

38
Q

loading dose formula

A

target concentration * VD /f

f can be ignored if IV

39
Q

true or false

the vd is different for every drug

A

true

40
Q

what is a useful indicator of renal function

A

creatinine clearance

41
Q

when drugs bind to tissues, is Vd higher or lower?

A

higher

42
Q

when drugs bind to plasma proteins, is vd higher or lower?

A

lower

43
Q

older people have decreased muscle mass and thus tend to have a _____ Vd of digoxin

A

smaller

44
Q

if a drug is highly lipid soluble, does vd increase or decrease?
give an example

A

increase
diazepam

45
Q

absorption usually occurs within the first _____ after a drug dose and varies according to food intake, posture, and activity

A

2 hrs

46
Q
A