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kinetics > midterm 1 > Flashcards

midterm 1 Flashcards

1
Q

what is manner in whihc drugs are taken?

A

dosage regimen

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2
Q

Definien pharmacokinetics

A

the stuyd of the fate of drug in the boyd

focus on:

ADME

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3
Q

define pharmacodynamisc

A

the effct of a drug in the body

  1. drug and recptor
  2. physiochemical or biochemical effects
  3. interaction of the drug
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4
Q

why study pharmacokinetics?

A

therpautic window

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5
Q

time course of a drug in body

A

drug in - plasma - receptor - intensity of effect - drug out

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6
Q

how do we meadure concentrations of drugs in blood

A

urine or blood

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7
Q

what assumptions do we make for one compartment model

A
  1. instanteous distrubution
  2. elmination and transpot follow firts order kinetics
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8
Q

what is the rate of change in the body dependent on?

A
  1. how much drug in reservois
  2. how well the drug is eliminated
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9
Q

how much drug is in resefovir depends on what?

A
  1. size of reservoir
  2. dose given
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10
Q

how well drug is eliminated depends on what?

A
  1. rate of elimination
  2. capacity of elimiating organs to remove drug
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11
Q

whats Cp0h

A

initial cocnentration

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12
Q

calcte of Cp0h

A

dose/ VD

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13
Q

what are the indpednet values?

A

Vd, CL, and dose

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14
Q

what does a large Vd indicate?

A

extensive distribution

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15
Q

path of a polar dug in body

A

stays in blood, low Vd

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16
Q

path of a weak base in body

A

lipophilic drug - has affinity for tissues therfore Vd is high

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17
Q

whats the samllest VD

A

plasma volume

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18
Q

types of elimination

A
  1. zero - order
  2. first order
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19
Q

elimiantion constant with time is what type?

A

zero order

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20
Q

what is k0

A

zero- order elimiantion rate constant

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21
Q

how do we expect zero order to look on linear vs semi-log paper

A

liner - straight line down

semi-log - curve down

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22
Q

whats a passsice diffusion - relate to order process, energy, driving force and species, competion and saturbilibyt

A
  • first order
  • no energy
  • driving force: gradient concentration
    specie: unionized
  • competition none
  • satuability none
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23
Q

whats a active diffusion - relate to order process, energy, driving force and species, competion and saturbilibyt

A
  • zero order
    -energy
  • driving force: carrier
    specie: unionized or ionized
  • competition
  • satuable
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24
Q

what is the rate of change in first order depednet on

A

K - eleimintion cinsant
and Concentration

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25
Q

what does first ordeer look like on linera vs semi log parp

A

liner- curved

semi-log - straight

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26
Q

unit for K

A

time-1

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27
Q

what is half life

A

the amount of time needed for a drug to drop to half it’s concentration

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28
Q

is half life consant or fluctutaion in first order?

A

consntnt

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29
Q

is half life consant or fluctutaion in zero order?

A

fluctuating

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30
Q

what is terminal half-life?

A

half-life of elimination phase

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31
Q

how long does it take for the body to be ride of 90% of a drug?

A

3.3 half lives

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32
Q

is K constant in zero order kinetics?

A

No

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33
Q

how do we calcaute half life

A

-.693/ K

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34
Q

what does AUC show?

A

total systemic exposure of the body to the drug

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35
Q

if we have high systemic exposure how would we expevct AUC to respond?

A

high AUC

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36
Q

units of AUC

A

amount*time/volume

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37
Q

CL units

A

volume/time

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38
Q

how can we get CL?

A
  1. K time VD
  2. Dose/AUC
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39
Q

using VD, CL what can we find?

A

half life, AUC, C0, K

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40
Q

tissues have their own make up whihc relates to what ocnepcts?

A
  1. blood flow
  2. cellualr makeup
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41
Q

what makes tissue less perfused?

A

high cell lipid cocnentration

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42
Q

what makes the tissue more perfused?

A

large concentration of durg metabolized by enzymes

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43
Q

when atlking about two compatrment models what are the two pirinicple steps?

A

distribution and elimination

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44
Q

how does Iv bolis in a two compatrment look

A

hockey stick

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45
Q

iv bolus in a one comeptment

A

just line decreasing

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46
Q

in a two-compartment where does blood travel first? then where? what are the elmination conatnts between trevel?

A

central compatment - blood Cp

Peripherla tissues - Ct

Cp- Ct k12
Ct - Cp k21

Emlimination from central comaptrment k 10 (K)

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47
Q

how do we travel between compartments?

A

via the concetration gradient

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48
Q

what is pseudoequilibirum

A

constnt ratio between drug in central and peripheral compartments

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49
Q

if we are trying to gage the cocnentration of a drug with it’s receptor in the central compatrment what is useful?

A

the plasma concentrations before or after pseudoequilibirum

50
Q

if we are trying to gage the cocnentration of a drug with it’s receptor in the periphaerl compatrment what is useful?

A

the plasma concentration only after pseudoequilibirum

51
Q

organs of central compatrment

A

plasma, liver, kidenys

52
Q

organs of pheripheral compartments

A

brain, musscle, adipose tissues

53
Q

for two compartment Iv bolus what’s an equation we can use to find concentration at a given time

A

C= A(to the power of -alpha time) + B(to the power of -beta time)

54
Q

distrubutaion phase is denoted by whihc greek alphabet

A

alpha

55
Q

elminaition phase is denoted by whihc greek alphabet

A

beta

56
Q

why would we feature in Iv bolus two compartment?

A

to find alpha of distributaion phase

57
Q

when i feater in iv bolus two compartment where is my A intercept

A

highest point where distrubution began

58
Q

how long does it take to reahc 90% of psuedo equilibirum?

A

3.3 half lives

59
Q

VD in central comaprtment calc ve in peripherla compartment calc - find on the formula sheet

A

slide 11

60
Q

Compartment model pros

A

-simplified approach to describe ADME
- monitor quantitivaly drug levle with urine or blood test
- can extract information
- useful for comaprison of pharmacokinetic agesnt

61
Q

Compatrment model cons

A
  • is empirical lacking ohysiological relevance
  • ## physiological models more relaistic
62
Q

when does drug cocnetration in the body decline?

A

when no more input

63
Q

what order of elimiantion does IV infusion follow and why?

A

zero - constant bc constant input

64
Q

what is steady state define as?

A

rate of input equals rate of output

65
Q

in iV ifsuion do we have a caontnt elemination rate?

A

yes it’s called K

66
Q

what dose k0 stand for? also denoted as ?

A

zero order input - rate of insusion can aslo be denoted as R

67
Q

at steady state does plasma cencetraion change?

A

no plasma concnetrtaion is constant at this point

68
Q

by defintion when can we assume we have reached steady state?

A

when 95% within Css

69
Q

what determines when we reach CSS

A

input is constant thus it depends of output of drug

70
Q

the time it takes to reach Css depends on what?

A

half-life whihc is a fucntion of output elimination

71
Q

how many half lives does it take to reach Css

A

3-5

72
Q

when Iv infusion is stopped how does elimination of drug orccue

A

in a firts order fashion

73
Q

what is the need for featuring in iv infusion?

A

it allows us to find the emlimination rate (K) for when insuion is stopped

74
Q

what equation is used for determining elmination once Iv infusion is stopped?

A

formula sheet change in C

75
Q

why would we need a laoding dose?

A

iv infusion takes 305 half lives to reach steady state however by using a loading dose we can increase the speed with whihc Css is achived

76
Q

when is infusion used?

A
  • emergmy
  • when other dosage forms are not tolerated
  • skips absorption step so quicker
77
Q

how do we calcualte loading dose?

A

slide 15 lecture 3

78
Q

most of the IV infusion we discuss is one or two compatment?

A

one compartment

79
Q

although the distrubution phase in Iv bolus is clearly define we don’t have a distributaion phase per say for iv infusion why?

A

in IV bolus all drug flow into cnetral compartment and distrubutes ti periphery. howeerv in infusion since there is a consnt drug suppply both central and periphery already have drug when infusion is stopped therefore there is a less sudden dip in drug level through out body since it’s already distrubuted however in Iv bolus disturbutaion still has to occur

80
Q

how does time to steady state change for iv infusion multi compartment

A

the equestion is still Css= (k0/ K X VD)
however the Vd must be that of the central comaprtemnt

81
Q

if we have a LD in Iv infuion mult compartment what will it look like ? what does it look like normally?

A
  • hockey stick - up down up
    normally one curve downwards starting from top
82
Q

what is Css level dependent on?

A

VD and CL parameters ZZ

83
Q

when are IV bolus and infsuion reserved for?

A
  • emergency when we need high drug concenn trations or rapid onset of action
84
Q

how are most drugs admintered? examples

A

through extravastion means sc, im, enema, supppository or oral ingestion

85
Q

what is the most commone route of adminstartion?

A

oral

86
Q

key step involved in oral?

A

absorption

87
Q

what elimination order is orla

A

first- order kinetics

88
Q

factors determing release and absorption of drug following oral adminstration of solide dosage form

A
  1. release characteristics of dosage form - disintegration, dissolution
  2. physiochemialc characteristics of drug
  3. physiology of GI tract
  4. abnormalities and disease of GI tract
89
Q

outline the path a oral drug takes through body

A

drug in product -(dissolution) - drug in solution - (intestinal absorption) - absorbed through drug in portal vein - active drug in systemic circulation

90
Q

what steps can limit rate of absorption?

A
  1. dissolution
  2. intestinal absorption
91
Q

what order processes are dissolution and disintegration?

A

first-order processes

92
Q

how does absorption in gut determine extent of absorption?

A

gut is very acidic, most absorption happens in intestines

however surface arae, pH and permebility play a role in absorption

93
Q

how does gastric emptying affect absoprtipn?

A

most drug are absorbed in intestine so we want fast gastric emptying

having slow gastric emptying can effect extent of absorption of other drugs

94
Q

what kind of foods can delay gastric emptying

A

fatty foods

95
Q

what factor is tied closely to first-pass effect?

A

oral biovailibility of drug or F

96
Q

how is F determined?

A

the systmeic drugs abvaialibilty determined determined by gut and hepatic clearnace

97
Q

define F

A

total fraction of doses that escape various barriers before entering systmic circualtion

98
Q

what value is F usualy

A

below 1

99
Q

What are the usual barriers we measure escaping?

A

gut
hepatic
feces

100
Q

effect of P-glycoportain or CYP450

A

lots of drugs are broken down by CYP 450 and my drinking grapefruit juice we inhibto this so drug can’t be broken down as easiy and there is lots in circulation

101
Q

what does oral admin grpah look like

A

start at zero then clim up to the point where ka=K and then gradual decline from that point

102
Q

before the peak of the oral admin curve what processes are occurring

A

absorption phase - consists of ka and K

103
Q

after the peak of the oral admin curve what processes are occurring

A

elimintaion - K

104
Q

when grpahing what’s on the x axis? Y axis?

A

time

concentration

105
Q

for oral explian a one compartment model of how the drug goes thru the body

A

drug (D) - passes through ka - into the plasma (Dp) - then is excreted (K)

106
Q

what is the rate of change defined by in the body for oral

A

rate of input - rate of output

input = D * ka
Output = K *Dp

107
Q

what is ka

A

absorption rate

108
Q

what is the intial C0 of a drug via oral

A

0

109
Q

what is Cmax represent in oral

A

where rate of absoprtion = rate of elimation

110
Q

what is t max depenedent on

A

drug in and drug out

indepednt from concentration

111
Q

how does chnages in the ka affect AUC?

A

doesn not effect

112
Q

how do chnages in the K effect AUC

A

inversely ralted

113
Q

why feature in oral dosing?

A

to determine the ka

114
Q

what is the flip flop phenomena?

A

when absorption ios slower then elmination (K) therefore the iv line intersects the oral line

115
Q

what does ka < < K mean?

A

this is extended or controlled release formulation meaning the rate of input is slower

116
Q

why is iv nescessary in oral grpahs

A

the Iv allows us to tell whether the terminal phase of the graph represents ka or K

117
Q

if ka» K

so iv is not parllry to terminl phase what does the terminal phase tlel us?

A

the terminal phase is then ka

118
Q

how do we determine that the terminal phase is K (elimination)?

A

we look at the iv in comparasion to the po.

if iv line is paralle to po then that is the K, otheriwse it’s the ka

119
Q

what is CLtb vs CLo?

A

CLtb - total body
- this takes into account F
- if iv F is 1, if oral we have a value

CLo - oral
- can get if we don’t know our F

120
Q

if we don’t know our F what clearance do we get?

A

CLo

121
Q
A
122
Q
A

kinetics (2 decks)

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