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PHAR 300 > Pharmacokinetics 1 > Flashcards

Pharmacokinetics 1 Flashcards

1
Q

what is pharmacokinetics

A

What body does to drugs

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2
Q

describe stages of pharmacokinetics

A

ADEM =
Administration or absorption
Digestion
Metabolism
Excretion

Some simultaneously because some distributed and also starting to metabolize it

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3
Q

what affects absorption of drugs

A

How we administer drug affects the absorption - has different properties
Impact duration of action and blood concentration of drug

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4
Q

name ways of administering medication

A

oral
Parenteral - injection
inhalation
topical
intraocular
sublingual

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5
Q

describe oral - general

A

enteral = easy, cheap, convenient = can do anywhere
Most desirable method
Lots of research on better ways to package them so you can swallow them

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6
Q

describe oral - research

A

Modified release tablets
Some very sophisticated
Ex = can be designed to restist acid in stomach and absorb in intestines
Drugs designed to dissolve slowly = slow release so action throughout day
Mixtures of drugs in one capsule
Clever ways to get drug to absorb
MANY VARIATIONS

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7
Q

describe oral - liver

A

first pass effect
All blood draining gastrointestinal tract first goes through liver
Fraction of drug you absorb through intestine will go through liver = different things can happen to it
Some drugs very highly metabolized = cannot take them orally

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8
Q

describe parenteral - general

A

Fast= do not have to wait for digestion
Accurate= since not broken down by liver
Can give same dose to everyone
bypass liver
Can be life saving

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9
Q

what do you have to be for injections

A

Must be sterile = can inject microorganisms into blood
Digestive system designed to deal with microorganisms

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10
Q

name and describe types of injections

A

intradermal = into skin
Subcutaneous = below skin
( must vary site if injecting frequently)
Intramuscular = into muscle
Intravenous = into vein (in hospital =vein cannulated for patients)
Intraperitoneal = into abdominal cavity
Intrathecal = Into cerebrospinal fluid

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11
Q

describe intraperitoneal injects more

A

Done in hospital
Useful for tumour = cancer
Can localize higher concentration of drug here
Can also have tube that is injecting drug - connected to pump

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12
Q

describe intrathecal injections more

A

Tumour in brain = many drugs cannot get into brain because of blood brain barrier
Have tube inserted into brain where tumour is

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13
Q

describe inhalation - general

A

Asthma, anesthetics, nicotine smokers
Many sites of action
Cigarette smokers inhale smoke for action on brain
Unless drug is specially designed to stay in lungs it will move into blood and to parts of body
Widely distributed

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14
Q

describe inhalation - inhalers

A

Large part swallowed and goes to gastrointestinal tract and liver
But small amount gets to lungs = enough to stop attack
But still gets into systemic circulation
Must have properties to stop systemic absorption if target is lungs

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15
Q

describe inhalation - systemic effects

A

Systemic effects rapid = seconds
For lungs - have huge surface area for all alveoli
Connection between alveoli and capillaries is intense = gas exchange, enormous and rapid
Get hit from nicotine within 7 seconds
Very effective - blood coming out of lungs goes straight to brain
Also for cocaine = systemic effects in minutes

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16
Q

describe topical

A

skin, mucosa
Drugs can be absorbed skin

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17
Q

give examples of topical medicines

A

Nicotine patches = designed to control amount and rate of absorption
Implants = contraception, can very slowly regulate specific drug release
Skin patch =
Designed so alllows drug in patch to be absorbed, Alters rate of absorption, Can slowly release drug over whole day, Also has depper absorption of the drug

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18
Q

what can many topical patches do

A

can control rate of drug absorption =
Microneedles that are soft, Won’t feel but goes into skin
Pumps to administer drugs
Can replace subcutaneous injection - research to try to do this

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19
Q

describe sublingual

A

Rapid
No first pass
High blood flow in mouth, warm moist location
Rapid absorption from this site
Does not go to liver first
Goes directly into circulation
Ex = chest pain nitroglycerine pill = very rapid

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20
Q

what does concentration of drug in blood depend on

A

way drug administered

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21
Q

INTRAVENOUS concentration of drug in blood

A

very high peak, straight into vein
Concentration comes down as distributed to rest of body

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22
Q

ORAL concentration of drug in blood

A

swallow and digest and goes to liver then blood
Longer to take effect
Concentration rises slower since metabolized by liver
Peak much lower

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23
Q

RECTAL concentration of drug in blood

A

rate of absorption smaller than oral
Still some into blood

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24
Q

name newer ways for administration

A

Smart capsules
Different shapes and sizes = alter rate of absorption
Replace needled - much research
Ultrasound patches = Facilitate absorption through skin
Insulin pumps

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25
Q

describe newer ways for administration - insulin

A

Tiny pumps that put on skin and will slowly monitor blood glucose and then infuse insulin at rate it is needed
Good for people with diabetes

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26
Q

describe newer ways for administration - capsules

A

Lipid capsule around= liposome
Nanocapsule
Lipid nanoparticle = mrna covid vaccines
Nanoparticles are area of research
Can be designed to target a specific cell type, be stable at 4 degrees celsius

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27
Q

define absorption

A

Transfer of drug from site of administration to blood stream (circulation)

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28
Q

what controls drug access

A

cell membranes

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29
Q

what do cell membranes have

A

tight junctions between cells so drugs cannot just slip in between cells

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30
Q

what can dissolved in cell membrane

A

Gases, hydrophobic molecules and small polar molecules can dissolve itself in membrane
Highly lipid soluble and go through
Oxygen, carbon dioxide, benzene, ethanol

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31
Q

what needs carriers to get through cell membrane

A

Large polar molecules and charged molecules
Get through by carrier mechanism
Glucose, amino acids
Need active transport to get into cell - needs energy
Also passive transport will various facilitated diffusion systems

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32
Q

what are most drugs designed as

A

Most drugs designed to be lipid soluble so can get easily absorbed into cells and reach target

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33
Q

describe stomach - oral administration - what it does

A

lands in stomach
not designed for absorption
Sterilizes food = hydrochloric acid kills microorganisms
Mainly stores food and then moves to intestine
Not major source of absorption
Some drugs can be absorbed because of highly acidic environment of stomach

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34
Q

describe unionized

A

lipid soluble = can dissolve in cell membrane

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35
Q

describe ionized

A

cannot cross = water soluble

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36
Q

describe what type of drug is more absorbed in stomach

A

Acidic drug is more unoinized in stomach = will be absorbed to some extent here but basic drug will not

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37
Q

describe weak acids

A

Non ionized form can diffuse through lipid membrane
In acidic environment more of acidic in unionized form

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38
Q

what happens in low vs high ph

A

In low ph - bases ionized
Not well absorbed in stomach
In high ph = acids ionized

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39
Q

when in ionized formed = …

A

low absorption

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40
Q

describe ph levels of digestive components

A

Saliva ~6
Stomach ~2
Intestine ~6-8
Blood ~7.4

41
Q

weak acid absorption

A

= more lipid soluble at low ph = stomach, easier to be absorbed

42
Q

weak base absorption

A

= more lipid soluble at higher ph = intestines, more rapidly absorbed

43
Q

give ex - absorption of antibiotic on empty stomach

A

Antibiotic = weak acid
So unionized in stomach and absorb quickly
If take antacid before or with milk = complex formed with drug and constituents in milk or antacid = slows rate of absorption and maximum concentration in blood

44
Q

what is purpose of intestines

A

Does not matter which type of drug = majority absorbed in intestines
Difference = Weak acids = some in stomach
Main purpose is absorption

45
Q

name absorptive areas of digestive system in meters squared

A

Oral cavity = 0.02
Stomach = 0.1-0.2
Large intestine = 0.5-1.0
Rectum = 0.04-0.07

46
Q

describe multiple absorptive mechanisms of intestines

A

All blood draining intestine must go to liver first
First pass metabolism
Mucosal metabolizing enzymes in intestines
Hepatic metabolizing enzymes in liver
Then blood circulates to rest of body
Portal venous circulation
How much absorbed in first pass of liver = depends on drug

47
Q

can all drugs be delivered orally?

A

Some drugs must be only delivered intravenously because so heavily metabolized in liver first pass so cannot give orally
Orally = continually recycled
High dose may cause toxicity
Sublingually = no first pass
Rectal = variable

48
Q

define bioavailability

A

fraction of drug administered reaching systemic circulation

49
Q

what is significance of bioavailability

A

dosage of drugs with high hepatic extraction
If high breakdown in liver = bioavailability 5-10%, may not be efficient
Low breakdown in liver = 90% bioavailability
varies from drug to drug

50
Q

what affects bioavailability

A

Route of administration

51
Q

describe intravenous effect on bioavailability

A

bypass liver
High initial concentration in blood
fall quickly - goes to liver and into tissues

52
Q

describe intramuscular effect on bioavailability

A

time lag from absorption into muscle
Peak not as high
Does not go to liver first

53
Q

describe sublingual effect on bioavailability

A

not as fast as muscle but still good
No first pass

54
Q

describe oral effect on bioavailability

A

Lowest
First pass

55
Q

define distribution

A

Transfer of drug from blood stream to other sites where they need to go

56
Q

describe drug - distribution

A

Free drug in extracellular fluids
All things happen = bound, broken down and gets to specific sites of drug action

57
Q

Distribution of IV anesthetic

A

Concentration in blood high then drops quick
Goes out ot blood and into tisssues
Brain and vsicera = High blood flow to brain and other areas, Need to affect neurons in brain for anesthesia
Lean tissues = Takes more time
Fat = Last place, Rate of blood flow in fat slower

58
Q

describe halothane redistribution

A

Halothane redistributuon
Blood flow varies between tissues and alters rate of distribution
Brain heart liver … muscle … fat, skin, bone, teeth, hair
Tissues rich in blood vessels = High concentration, High blood flow, Shows up first, Decreases when gone
Medium blood vessels = slower
Poor concentration of blood vessels = Longer to accumulate and longer to get rid of it

59
Q

how does free drug get distributed

A

Free drug has to get out of circulation and be distributed into body
variety of places

60
Q

where can free drug go

A

Can go to therapeutic site - to get drug action
Can be bound to receptors - can be bound multiple times
Can be bound to other things = end up in tissue reservoirs like muscle and fat
Only free drug is able to get out of blood and get to other sites (Can be bound and free in plasma)
Can get to unwanted sites of action = side effects
Can be broken down as blood flows through liver repeatedly
Can also be excreted

61
Q

describe drug fate in tissues - general

A

Drugs bound to protein will not get out of circulation, only free drug can
May get bound to protein in tissues sites then cannot move around more (Has to be in soluble form to cross membrane and get into cells)

62
Q

describe drug fate in tissues - metabolism

A

Some drugs metabolized by cells
Like liver cells
Drug metabolites can also go out into circulation

63
Q

describe drug fate in tissues - free drug

A

Free drugs that are lipid soluble can cross membranes
Can be transported and can bind and metabolites can occur in other tissues

64
Q

how can drugs pass

A

diffusion or facilitated diffusion (passive) or by active transport

65
Q

describe Properties affecting tissues permeability

A

Drug bound to protein cannot cross capillary wall because its too big
If very small = drugs less than 50 daltons, Can pass through pore in capillary wall and then same thing and get into cell membrane - bulk flow
Highly lipid soluble = Can cross capillary wall and cell membrane, Lipophilic drugs = 50-600 daltons, Passive diffusion
Highly polar = not soluble, Polar or ionized drugs of side greater than or equal to 50 daltons, Active transport

66
Q

describe peripheral capillary - what can pass through

A

Lipid soluble substances can pass through endothelial cells (capillary is one endothelial cell thick)
Small water soluble substances pass through prores
Exchangeable proteins are moved across by vesicular transport (Transport systems)

67
Q

what can alter drug distribution

A

Disease can alter drug distribution
Cancer = tumour alter properties of blood vessels that supply tumour
Can make drugs have less access or greater

68
Q

what is ideal for administering drug

A

Must have gap before effect
Minimal effective concentration for therapeutics
Want mount in blood to be above this but below circulating concentration that gives what therapeutics
Want concentration to be in therapeutic window

69
Q

what do Variables affecting drug concentration alters

A

rate and height

70
Q

describe variables affecting drug concentration

A

Faster elimination,Problem = so not very effective since eliminates quick
Effective for short period of time
Faster absorption = greater
Larger dose = Can get to maximum concentration in blood which is bad

71
Q

describe blood brain barrier

A

Capillaries in brain have no spaces between endothelial cells

72
Q

describe blood brain barrier
features

A

Have tight junctions in between
Hard for drugs to get into brain
Also astrocytes with foot processes up against wall of capillary in brain
Effective at keeping things out usually

73
Q

blood brain barrier length

A

Human brain capillaries = 400 miles, very complex

74
Q

when can Blood brain barrier can be impaired

A

Newborns = not fully effective, less than 6 months old, Need to dose them properly
Infections = Meningitis, Not as effective, Things can get into brain that are not supposed to

75
Q

what else protects brain

A

Also have blood cerebrospinal fluid barrier

76
Q

Where is csf made

A

Cerebrospinal fluid made in choroid plexus - also monitors what gets into csf

77
Q

describe csf and brain pathway - get in

A

If something is in csf = can get to brain easily
Drug in circulation → free drug can get out of circulation→ cerebral spinal capillaries with tight junctions (drug has to be highly soluble and have properties that allow it to cross blood brain barrier) → then circulates throughout brain and can act on various cells (neurons and glia)

78
Q

describe csf and brain pathway - get out

A

Can get out through cerebrospinal fluid
Continually formed and circulating and leaving
Takes out metabolites and drug goes through csd then venous sinuses and goes back to circulation and broken down by liver

79
Q

name a special tissue we need to consider effect of drugs on

A

Special tissue = placenta
Not an effective barrier
may slow down transfer of drug to fetus though
Lipid soluble drugs can rapidly pass
Water soluble drugs pass slowly
Some drugs can concentrate in fetus
Use caution when pregnant
Must check with doctor

80
Q

describe protein binding in circulation

A

If bound = cannot get out
Mainly albumin bound to drug
Some glycoproteins

81
Q

describe protein bound fraction

A

remains in blood and cannot go anywhere
Has to be free to be transferred to site of action or to be stored in tissue reservoirs

82
Q

can proteins in circulation be altered

A

Proteins in circulation can be altered

83
Q

give examples of when proteins in circulation altered

A

Albumin impaired in liver disease = Liver is site of plasma protein synthesis - albumin
Glycoproteins - elevated in inflammation
Occasional drug interaction = displacement, Drug can replace another drug from binding to plasma proteins, Pretty rare since usually excess albumin but can happen = enough to go around for all drugs in system

84
Q

name models of distribution

A

one compartment
two compartment

85
Q

describe one compartment model of distribution

A

Distribute equally everywhere
Reality is More complex than this

86
Q

describe two compartment model of distribution

A

Immediately after administration = concentration of drug higher in tissues with more blood flow
Brain, lungs, heart, liver
After distribution = equilibrium everywhere

87
Q

describe p glycoprotein

A

transports drugs out of cell
Very effective
Ex = drug can cross membrane (soluble) but p ejects from cell immediately
Hard sometimes = for cancer

88
Q

compare distribution vs elimination

A

Distribution = Sharp decline at beginning = blood being redistributed out of blood
Elimination = Slow decline as blood continuously flows through liver

89
Q

describe volume of distribution

A

where does it go
Peripheral volume = everything else
Central volume = blood
Over time drug will get distributed
Volume of distribution = Vd

90
Q

describe Vd

A

Amount of drug in body / concentration in plasma
Amount = what you gave

91
Q

what are variations in Vd due to

A

Properties of drug
Protein binding =How much bound in circulation
Tissue binding = How much bound in tissue

92
Q

what is avd

A

Apparent volume of distribution = AVD
APPARENT RATHER THAN ACTUAL VOLUME

93
Q

Calculations for Vd

A

Vd = X/Cp
Quantifies distribution
Relates drug concentration (Cp) to amount of drug in body (X)
Gives information on the amount of drug distributed into tissues = where drug is

94
Q

when is avd small

A

If drug mainly found in circulation= avd small = mostly still in blood
High protein binding = high concentration in blood = low avd

95
Q

when is avd large

A

If drug mostly out of blood = avd large
Low concentration in blood = know most of drug has gone out of blood and is taken up elsewhere
High tissue binding = low concentration in blood = high avd

96
Q

what can we use to calculate loading dose

A

avd - tissue binding vs protein binding

97
Q

what is loading dose

A

How much drug you have to give to get certain amount in concentration

98
Q

describe volume of distribution - gen

A

Varies a lot between different drugs
Just tells you where drug has gone
Can be distributed through total body water or extracellular fluid

PHAR 300 (9 decks)

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