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Pharmacology > Lecture 2 & 3 - Pharmacokinetics (PK) and Drug Disposition > Flashcards

Lecture 2 & 3 - Pharmacokinetics (PK) and Drug Disposition Flashcards

1
Q

Pharmacokinetics

A

what the body does to a drug

*study of how the body absorbs, distributes, metabolizes, and eliminates (ADME) a drug over time

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2
Q

ADME ?

A

Absorption
Distribution
Metabolism
Elimination/Excretion

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3
Q

Where does 1st pass effect occur?

A

stomach

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4
Q

Primary site for absorption?

A

small intestine

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5
Q

____ ______ is key for distribution

A

blood stream

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6
Q

Primary site for metabolism?

A

liver

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7
Q

Primary site of excretion

A

kidney

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8
Q

What is the clinical goal from using and understanding pharmacokinetics?

A
  • enhance efficacy

- decrease toxicity

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9
Q

Drug effect related to concentration at ??

A

site of action

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10
Q

For more drugs, the concentration at the site of the _____ determines the intensity of a drug’s effect

A

receptor

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11
Q

In order for drugs to move through the body they must cross cell membranes. What are the 3 ways they can do that?

A

1-pass through channels or pores

2-passing through the membrane with the aid of a transport system

3-penetrating directly

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12
Q

Where are transporters found?

A

liver
kidneys
intestines
brain capillaries

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13
Q

Out of the 3 types of drug movement, which is the most common?

A

direct penetration

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14
Q

Why does the movement through the body for most drugs depend on ability for direct penetration? (2 reasons)

A
  • most drugs are too large to pass through channels

- most drugs lack transport system to help them cross cell membranes

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15
Q

In order to penetrate cell membranes directly, a drug must be _____

A

lipophilic

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16
Q

Difference between one and two compartment model?

A

One-compartment model:
-drug is administered, immediately distributed, and then can be metabolized and excreted

Two-compartment model:

  • some drugs do not distribute instantaneously to all parts of the body
  • it goes to individual organs first, and then gets distributed to the peripheral part of the body afterwards
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17
Q

Drugs that don’t extensively distribute into extravascular tissues (drugs that aren’t stored) are well described as ?

A

one-compartment models

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18
Q

Drugs that do extensively distribute into tissue (drugs that are stored in tissues) are well described as ?

A

two-compartment models

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19
Q

bioavailability (absorption)

A

fraction of unchanged (unmetabolized) drug reaching the systemic circulation following administration by any route

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20
Q

drug accumulation

A

inversely proportional to dose lost

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21
Q

Vd (volume of distribution)

A

measure of apparent space in the body available to contain the drug - how the drug is distributed in the body relative to plasma

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22
Q

clearance refers to ???

A

metabolism and excretion

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23
Q

Clearance (metabolism and excretion)

A

measure of ability of the body to eliminate the drug

volume of drug per unit of time that gets excreted

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24
Q

drug half life (T1/2)

A

time required to change the concentration of the drug present in the body by one half during elimination

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25
Q

Formula for:

bioavailability

A

AUC admin route / AUC(IV) x 100

OR

AUC oral / AUC injected x 100

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26
Q

Formula for:

drug accumulation

A

accumulation factor = 1/dose lost

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27
Q

Formula for:

Vd

A

amount of drug in body (mg) / conc of drug in plasma (mg/L)

answer expressed in L

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28
Q

Formula for:

clearance (Cl)

A

Cl = (0.693 / t1/2) x Vd

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29
Q

Formula for:

drug half life (T1/2)

A

t1/2 = (0.693 X Vd) / Cl

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30
Q

bioavailability (absorption) is the transfer of drug from ______ to ______

A

site of administration

to

bloodstream

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31
Q

When looking at a graph of time vs plasma concentration (Cp) - how do you determine bioavailability?

A

it is the area under the curve (extent)

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32
Q

When looking at a graph of time vs plasma concentration (Cp) - what does the time to reach peak concentration represent?

A

rate

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33
Q

When looking at a graph of time vs plasma concentration (Cp) - what does the peak concentration represent?

A

rate and extent

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34
Q

IV has what % Bioavailability

A

100%

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35
Q

IV has the ___ onset of any drug admin

A

fastest

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36
Q

What other route also has a very fast onset?

A

inhalation

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37
Q

List 3 limitations for drug absorption?

A 
tissue perfusion (blood flow)
diffusion-limited absorption
first pass effect
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38
Q

What is first pass effect?

A

basically this is mainly a concern for drugs taken orally

and what happens is the the liver metabolizes a portion of the drug before it can be effective

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39
Q

What is enterohepatic cycling?

A

It provides an opportunity for the body to recycle the drug that hasn’t had a chance to be metabolized

If it didn’t get metabolized the 1st time it can get metabolized the 2nd or 3rd time around through enterohepatic cycling

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40
Q

Enterohepatic cycling reduces _____

A

elimination

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41
Q

Enterohepatic cycling prolongs

A 
half life 
(drug stays in body longer)
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42
Q

List 8 factors influencing drug absorption

A

1) formulation
2) water solubility
3) lipid solubility
4) pKa
5) GI motility
6) posture (laying down or standing up)
7) other drugs/foods (possible interactions)
8) gastric pH

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43
Q

acidic drug is ____ in acid media

A

non-ionized

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44
Q

acidic drug is ____ in alkaline media

A

ionized

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45
Q

drug accumulates when ??

A

doses are repeated

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46
Q

How many half lives does it take to 100% accumulate?

A

at least 4

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47
Q

When is a steady state achieved?

give an example

A

When rate of drug elimination = rate of administration.

Example - IV

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48
Q

does frequent vs infrequent dosing affect steady state plasma concentration?

A

no - see diagram

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49
Q

_____ is protein most common for bound drug

A

albumin

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50
Q

only ____ drug can leave vessels

A

unbound (because bound drugs are too big)

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51
Q

high Vd = ?

A

drug is more distributed outside the plasma concentration

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52
Q

low Vd = ?

A

more blood in plasma concentration (less distributed)

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53
Q

What 2 things is Vd needed for determining?

A

clearance

loading dose

54
Q

Formula for:

loading dose

A

loading dose = Vd x TC (target/desired concentration) / F

f = fraction absorbed
bioavailability

55
Q

What is a loading dose?

A

it immediately allows drug to get within the therapeutic range

(whereas without a loading dose - it could take longer)

56
Q

Formula for:

dosing rate

A

Cl x TC (target concentration)

vol/time) (amount/vol) = (amount/time

57
Q

Formula for:

maintenance dose

A

(dosing rate / F) x dosing interval

(amount/time) (time) = amount

58
Q

First order rxns show a ____ graph

A

radical

59
Q

Zero order rxns show a ____ graph

A

straight/constant

60
Q

most drugs are ___ order rxn

A

first

61
Q

When determining the order of a rxn, what are the x and y values on the graph?

A 
x = conc of drug
y = rate of drug metabolism
62
Q

Give an example of a drug that under goes metabolism in a zero order rxn

A

phenytoin

63
Q

acidic drugs are more likely to be concentrated in ____ compartment

A

blood

64
Q

basic drugs are more likely to be concentrated in ____

A

tissue

65
Q

describe phase 1 metabolism

A

drug is changed into modified drug by adding/exposing functional groups through:

oxidation
hydrolysis
reduction

66
Q

describe phase 2 metabolism

A

modified drug is changed into modified drug-conjugated through:

glucuronidation
sulfation
(glutathione) acetylation

67
Q

First order: rate of drug metabolism _____ to dose

A

proportional

68
Q

Zero order: rate of drug metabolism remains ____ over time

A

constant

69
Q

Clearance is needed for determining ?? (2)

A

dosing rate

maintenance rate

70
Q

define clearance

A

the volume of plasma that would contain the amount of drug excreted per unit time (minutes)

71
Q

for a drug to accumulate?

A

at least 4 half lives (90%)

72
Q

for a drug to eliminate?

A

4-5 half lives (97%)

73
Q

Low MW drugs enter kidney via renal artery and ____ soluble drugs move back into the blood

A

lipid

74
Q

non-lipid soluble, polar, and ionized drugs remain in ____

A

urine

75
Q

What are the 3 steps to renal elimination?

A

glomerular filtration
tubular secretion
tubular reabsorption

76
Q

What is used to assess renal impairment?

A

creatinine clearance

77
Q

____ CrCl = kidney not working properly

A

high

78
Q

aging has a ____ effect on T1/2

A

decreasing

79
Q

obeying has an ____ effect on T1/2

A

increasing

80
Q

pathologic fluid has an ____ effect on T1/2

A

increasing

81
Q

induction of CYP450 has a ____ effect on T1/2

A

decreasing

82
Q

inhibition of CYP450 has an ____ effect on T1/2

A

increasing

83
Q

organ failure has an ____ effect on T1/2

A

increasing

84
Q

OAT = ?

A

organic anion transport (proteins)

85
Q

OCT = ?

A

organic cation transport (proteins)

86
Q

OATs and OCTs belong to?

A

SLC (super family)

-soluble carrier transporters

87
Q

3 types of drug transporters?

A

-OATs
-OCTs
-P-glycoprotein (P-gp or MDRs)
(multi-drug resistance-associated proteins)

88
Q

___ is a vehicle for drugs being metabolized

A

bile

89
Q

major route for drug elimination?

A

renal excretion

90
Q

bile excretion favours compounds with a higher __

A

MW

91
Q

hepatic drug metabolizing enzymes are known as the ____ system

A

P450

92
Q

P450 system consists of __ families

A

12

93
Q

__ of these 12 enzyme families metabolize drugs (CYP 1,2,3)

A

3

94
Q

__ of these 12 families metabolize steroids and fatty acids

A

9

95
Q

CYP ____ has the same #

A

family (ex. CYP1)

96
Q

CYP _____ has the same # and letter

A

subfamily (ex. CYP1A)

97
Q

CYP _____ has the #, letter, #

A

gene/isoenzyme

98
Q

ox = ?

A

losing electrons

99
Q

red = ?

A

gaining electrons

100
Q

inhibitors and inducers affect?

A

half life mainly (but also all those other parameters)

*metabolizing enzyme is being influenced

101
Q

enzyme inducers affect metabolism how?

A

speed up metabolism

102
Q

enzyme inhibitors affect metabolism how?

A

slow down metabolism

103
Q

pharmacokinetics of metabolism inducer?

A

affects concentration, increased clearance, decreased half life

104
Q

pharmacodynamics of metabolism inducer?

A

measures the drug effect (response)

105
Q

an inhibitor ____ drug metabolism

A

blocks (stops)

106
Q

an inhibitor therefore causes an ____ response (PD)

A

increased (you are blocking metabolism/ breakdown of the drug so therefore drug stays in body and will have a higher response)

107
Q

an inhibitor causes an ____ plasma t1/2 life (PK)

A

increased (you are blocking metabolism of the drug so it stays in body longer = therefore higher half life)

108
Q

an inhibitor’s effects are ____?

A

immediate

109
Q

an inducer causes ____ drug metabolism

A

increased

110
Q

therefore an inducer causes ___ drug response (PD)

A

decreased (you are speeding up metabolism so therefore drug will be broken down at a faster rate and there will be less left over to create a drug response)

111
Q

an inducer causes ____ plasma t1/2

A

decreased (drug is leaving body faster = therefore decreased half life)

112
Q

an inducer’s effects are ____

A

delayed

113
Q

PK affects ??

A

concentration of the drug

114
Q

PD affects ???

A

the drug’s affect/ response

115
Q

aspirin + warfarin = ?

A

hemorrhage

116
Q

erythromycin + seldane = ?

A

fatal arrhythmia

117
Q

CNS depressant + CNS depressant (ex. alcohol) = ?

A

respiratory depression (could be even death)

118
Q

viagra + nitroglycerin = ?

A

fatal hypotension (drop in BP)

119
Q

ACE inhibitors + K-sparing diuretics = ?

A

hyperkalemia (higher than normal levels of potassium)

120
Q

example of enzyme inhibitor

A

cimetidine

121
Q

What is cimetidine-H2 receptor antagonist used to treat?

A

peptic ulcer

122
Q

Possible drug interactions with cimetidine-H2 receptor agonist?

A

warfarin
benzos
phenytoin
morphine

123
Q

drugs are designed for what type of metabolizer?

A

extensive metabolizers

124
Q

if you’re a poor metabolizer what are you at risk of?

A

increased toxicity

125
Q

if you’re an ultra extensive metabolizer what are you at risk of?

A

reduced response

126
Q

_____ have highest frequency of PM phenotype

A

caucasians

127
Q

_____ have highest frequency of IM phenotype

A

asians

128
Q

_____ have highest frequency of UM phenotype

A

africans

129
Q

more copies of allele that is expressive to the enzyme means ?

A

more metabolism

130
Q

List the 6 things that can cause variations in drug metabolism

A 
induction
diet
inhibition
genetics
development
disease
131
Q

rate of drug disposition is impaired in what age groups

A

very young

very old

Pharmacology (21 decks)

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