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second year > LS5003 TB1 (Dr Piper) > Flashcards

LS5003 TB1 (Dr Piper) Flashcards

1
Q

define drug disposition

A

disposition refers to what happens to the drug after it enters the body,

(i.e. excluding absorption)

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2
Q

wht is the abbreviation used for drug diposition

A

Administration

Distribution

Metabolism

Eexcretion

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3
Q

define bioavailiability (F)

A

the fraction(F) of administered dose that reaches the systemic circulation

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4
Q

what F value does intravenous injection give

A

1 (100%)

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5
Q

what does BioA mean

A

bioavailability = the measure of the fraction of an administered drug which reaches systemic cirulation

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6
Q

define pharmacokinetics

A

the way the body affects the drug

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7
Q

define clearance

A

how much is being removed from the body per unit of time

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8
Q

define pharmacodynamics

A

the way the drug affects the body

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9
Q

what does pharmacokinetics consist of?

A

.absortion .metabolism .distribution .excretion

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10
Q

how is the therapeutic (window) index calculated

A

TD50 / ED50

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11
Q

define ED50

A

Effective dose producing 50% response in population

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12
Q

define TD50

A

toxic dose in 50% of population

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13
Q

with therapuetic index, is bigger better or worse?

A

better

there are also no units

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14
Q

define therapeutic index

A

a measure of its selectivity in producing theraputic effects rather than unwanted effects

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15
Q

give the units for

milli

micro

nano

pico

femto

A

m 10-3

u 10-6

n 10-9

p 10-12

f 10-15

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16
Q

whats avagadros constant

A

6 x 1023 atoms/molecules

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17
Q

define molarity (M)

A

number of moles of a substance dissolved in 1 litre of water

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18
Q

convert 2uM to pM

A

2uM = 2,000,000pM

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19
Q

what are agonists

A

any drug (or exogenous/endogenous substance) that binds to a receptor and activates it to cause a response

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20
Q

define Kd

A

drug conc reaquired for 50% receptor occupancy

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21
Q

Bmax

A

100% receptor occupancy

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22
Q

define EC50

A

effective conc causing 50% of max effect

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23
Q

Emax

A

maximum effect a drug can have either in a tissue/ organ/ whole organism

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24
Q

drug efficiancy

A

maximum effect a drug can produce regardless of the dose i.e. max effect achievable

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25
Q

drug potency

A

the concentration of drug needed to produce a given effect

e.g. increase heart rate by 5 beats per minute

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26
Q

why could EC50 and Kd be different in some tissues

A
  • we dont know how muc of a drug dose actually reaches the receptors (some could be degraded by the body/ taken up by other tissues)
  • there may be ‘spare receptors’ in tissues
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27
Q

do ‘spare receptors’ differ strucurally?

A

no, structurally identical

they are just an excess

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28
Q

how could you tell if there spare receptors (2 ways)

A

EC50 usually lower than Kd

adding an irreversible antagonist i.e. blocking a proportion of the receptors does not always affect he max response

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29
Q

fill in this diagram

A
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30
Q

whats meant by drug translocation

A

movement of a drug into circulation

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31
Q

drug absorbtion can be described in terms of

A

rate and extent

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32
Q

list the 4 principle mechanisms of drug translocation

A

1) diffusion through lipid
2) diffusion through aqueous channel
3) carrier
4) endocytosis

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33
Q

in diffusion through lipids

  • do most drugs diffuse this way
  • what drugs can?
  • dependent on what?
A
  • yes most drugs so diffuse this way
  • only small lipid soluble, non-polar/ non-ionised drugs
  • dependent on S/A and blood flow
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34
Q

what law corresponds to diffusion through a lipid layer

A

fick’s law

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35
Q

whats the criteria for rapid permeation (lipid diffusion)?

and what are these two criterias mesured by?

which of these are most important in lipid diffusion?

A
  • drug molecules must be presetn in membrane in sufficient numbers (partition coefficient)
  • drug molecules must be mobile within the membrane (diffusion coeficient)

Partition coefficient = most important for lipid diffusion

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36
Q

partition coefficiernt =

A

ammount of drug in lipid phase / ammount of drug in aqueous phase

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37
Q

in diffusion through aqueous pores/ion channels

  • how does it move
  • what molecules can travel this way
  • 2 examples
  • is it a common mechansim for drugs
A
  • high to low conc
  • small water soluble molecules of less than 100 Da
  • lithium (bipolar disorder), radioactive iodide (thyroid overactive)
  • no, not major route for drug permeation
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38
Q

what are the 2 types of carrier mediated transport?

how do these differ?

what important sites contin these mechansims

A

active transport and facilitated diffusion

active= ATP required as agaisnt conc gradient facilliated = no ATP required

renal tubule, blood-brain barrier, GI tract

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39
Q

what are the 2 types of solute carrier transporters (SLCs), give 1 example of a drug that uses these

A
  • organic anion transporter (OAT), antibiotics
  • organic cation transporter (OCT), quinine, cisplatin. cimetdidine
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40
Q

what are the active trasnpot mechanisms ofter reffered to as?

give 2 examples of drugs recognised by these mechanisms

A

ATP-binding cassette (ABC) transporter

digoxin, quinidine

41
Q

name a drug that utilised the carrier mediated transport mechanisms for

facilitated diffusion: -

active transport: -, -

A

facilitated: L-dopa used in parkinsons disease
active: penicillin in renal tubule, 5-fluoruracil (anticancer drug)

42
Q

endocytosis normally concerned in the uptake of what molecules?

what types of drugs can permeate via this route?

example:?

attempts to utilise it as targeted drug uptake mechanism?

A
  • macromolecules
  • large molecular weight (1000Da or more)
  • insulin crossing blood brain barrier
  • incorporating the drug into lipid lipsomes
43
Q

name the 6 physiochemical factors affecting drug absorbtion

A
  • molecular weight
  • particle size
  • physical nature of drug
  • drug partition coefficient
  • salt form of drug
  • polymorphism and amorphism
44
Q

when does molecular weight affect drug absorbtion?

A

when drug is absorbed via passive diffusion

45
Q

define micronisation

A

process that helps reduce particle size to that in the range of micrometes or nanometers improving absortion of poorly soluble drugs

46
Q

the physical nature of drugs is that most drugs are weak acids or bases. Therefore will exhibit ?

are ionised species lipid soluble?

A

pH dependent ionisation

No

47
Q

define pKA

A

ionisation constant, equal to pH at which 50% of drug is ionised

48
Q

Write the ionisation equations for weak acids and bases and state which sides of the equation are ionised and which are non-ionised

A
49
Q

state the henderson-hasselbach equations for both weak acids and weak bases

A
50
Q
A
51
Q
A
52
Q

define lipinski’s rule of 5

A

rule of thumb that describes the “drugablilty” of a molecule.

determines if molecule has the chemical and pjysical porperties that allow it to be orally active.

53
Q

What are the 4 categories of lipinkis rule of 5

A

1) molecular weight under 500Da
2) Octantol: water partition coefficient (logP) that does not exceed 5
3) no more than 5 hydrogen donors
4) no more than 10 hydrogen acceptors

54
Q

name the 5 compartments the body can be visualised as which the drug can distrubute into, including their % of body weight they make up:

A
  • plasma (5%)
  • interstitial fluid (16%)
  • intracellular fluid (35%)
  • transcellular fluid (2%)
  • Fat (20%)
55
Q

based in a 70kg person, what are the average litres of each of these fluids:

  • plasma
  • intracellular
  • interstitial water
  • extracellular water
  • total body
A
  • 3L
  • 27L
  • 12L
  • 15L
  • 42L
56
Q

define Vd

A

the volume of plasma that would contain the total body drug content at a concentration equal to plasma concentration

57
Q

whats the equation for Vd?

A

Vd = D / Cp

58
Q

what does the Vd value indicate?

A

where the drug is most likely to be distributed in the body

59
Q

any drug with a Vd of over around 50-60L indicates what?

A

tissue binding

60
Q

what will tissue binding do to the apparant concentration in Vd calculations

A

artificially lower the concentration to less than expected due to drug binding to tissue

61
Q
A
62
Q
A
63
Q
A
64
Q
A
65
Q

what 2 factors effect the rate of distribution

A

rate: -membrane permability
- blood perfusion

66
Q

what factors effect the extent of distribution:

A
  • lipid solubility
  • degree of ionisation
  • plasma protein binding
  • intracellular binding
67
Q

what 2 factors effect membrane permeability:

A
  • dependent on charcteristics of the organ membrane
  • membranes have varying pore size
68
Q

at therapeutic concentrations most drugs show binding to plasma proteins. what percentage of drug tends to bind to plasma proteins

A

99% bound,, 1% free

69
Q

drug binding to plasma proteins

total drug =

A

bound drug (Fb) + free drug (Fu)

70
Q

the amount of binding to plasma proteins is dependent on what factors?

A
  • free drug conc
  • affinity of the drug for the binding site
  • plasma protein conc
71
Q

in the case of plasma proteins (albumin) how many binding sites to which the drug can bind do they typically have?

A

1-4 sites

72
Q

what is the dispositional signifcance of binding?

A
  • allows transport of more drug than would be predicted from its aqueous solubility (plasma)
  • acts as a reservoir (compartments) which helps to prolong the action of drugs
  • however only drug which is not bound to plasma protein can produce pharmaclogical effect
  • bound drug cannot pass membranes
73
Q
A
74
Q
A
75
Q

what types of drug can pass from the mother to the foetus?

A

-lipid soluble drgs

76
Q

what placental characteristics can determine drug transfer

A
  • placental bloodflow
  • placental transport machanisms
  • placental metabolism
77
Q

how does foetal plasma preotein levels differ form the mother?

A

albumin is more concentrated

78
Q

how does foetal blood pH differ from maternal blood pH

A

foetal blood has a lower pH

79
Q

what are the 6 things that influence rate and extent of distribution

A
  • membrane permeability
  • blood perfusion
  • lipid solubility
  • degree of ionisation
  • plasma protein binding
  • intracellular binding
80
Q

what is biotransformation?

A

few drugs are eliminated from the body unchanged. most undergo biotransformation. this means a chemical modification inside an organism, usually turning non-polar molecules polar to stop reabsortion in the renal tubules, allowing excretion.

81
Q

what are the sites of metabolism for drugs;

A
  • liver
  • kidney
  • lungs
  • skin
  • intestine
82
Q

what is the primary process of metabolism

However in certain instaces:

1) drugs can be?
2) metabolism can produce?

A

to change a drug into more water soluble molecules (increases polarity to aid excretion)

1) drugs can be activated by metabolism. These are termed pro-drugs
2) metabolism can produce more active metabolites which contribute to the action of the drug

83
Q

what are pro-drugs?

give an example?

A

A prodrug is a medication or compound that, after administration, is metabolized into a pharmacologically active drug.

e.g. L-dopa

84
Q

what are phase 1 metabolism reactions

A
  • parent drug is converted into a more polar molecule
  • achieved by either introduction of or unmasking of a polar functional group
85
Q

what are phase 2 reactions

A
  • involves conjugation reactions
  • occur ar polar groups introduced/unmasked during phase 1 reactions
  • reactions tend to produce an inactive and very water soluble moelcules
  • excretion then follows, mainly by the renal route
86
Q

are metabolism phase 1 reactions catabolic or anabolic

A

catabolic

87
Q

what are the 5 types of phase 1 reactions

A

aromatic hydroxylation

hydroxylation

dealkylation

deamination

desulphuration

88
Q

what is the most important enzyme for metabolic reactions

A

microsomal miced function oxidase

89
Q

what is cytochrome P450 and what does it do

A
  • a haem protein
  • forms part of electron transfer system
  • binds: molecular oxygen, substrate (ie parent drug)
  • exists in many isoforms with different substrate specificity
90
Q

name the 3 non microsomal mixed function oxidase phase 1 reactions

A

A.oxidative reactions

B.reductive reactions

C.Hydrolytic reactions

91
Q

Phase 2 reactions occur mainly where?

A

-liver

92
Q

what type of reaction are phase 2 reactions, and where on the molecule do they occur

A

conjugation reactions which occur at polar groups

93
Q

what is the most common phase 2 conjugation reaction?

A

glucoronidation

94
Q

whats meant by first pass metabolism

A

metabolism of drug before it reaches systemic cirulation

95
Q

sites of first pass metabolism

A

liver

intestinal wall

96
Q

whats extraction ratio

whats the formula for it

A

measure of hepatic clearance

CLliver / Q

Q = hepatic blood flow

97
Q

Drug interactions, in drug metabolism, can occur via what 2 mechanisms

A

enzyme induction

enzyme inhibition

98
Q
A

second year (6 decks)

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