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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
describe newer ways for administration - insulin
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
26
describe newer ways for administration - capsules
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
27
define absorption
Transfer of drug from site of administration to blood stream (circulation)
28
what controls drug access
cell membranes
29
what do cell membranes have
tight junctions between cells so drugs cannot just slip in between cells
30
what can dissolved in cell membrane
Gases, hydrophobic molecules and small polar molecules can dissolve itself in membrane Highly lipid soluble and go through Oxygen, carbon dioxide, benzene, ethanol
31
what needs carriers to get through cell membrane
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
32
what are most drugs designed as
Most drugs designed to be lipid soluble so can get easily absorbed into cells and reach target
33
describe stomach - oral administration - what it does
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
34
describe unionized
lipid soluble = can dissolve in cell membrane
35
describe ionized
cannot cross = water soluble
36
describe what type of drug is more absorbed in stomach
Acidic drug is more unoinized in stomach = will be absorbed to some extent here but basic drug will not
37
describe weak acids
Non ionized form can diffuse through lipid membrane In acidic environment more of acidic in unionized form
38
what happens in low vs high ph
In low ph - bases ionized Not well absorbed in stomach In high ph = acids ionized
39
when in ionized formed = ...
low absorption
40
describe ph levels of digestive components
Saliva ~6 Stomach ~2 Intestine ~6-8 Blood ~7.4
41
weak acid absorption
= more lipid soluble at low ph = stomach, easier to be absorbed
42
weak base absorption
= more lipid soluble at higher ph = intestines, more rapidly absorbed
43
give ex - absorption of antibiotic on empty stomach
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
what is purpose of intestines
Does not matter which type of drug = majority absorbed in intestines Difference = Weak acids = some in stomach Main purpose is absorption
45
name absorptive areas of digestive system in meters squared
Oral cavity = 0.02 Stomach = 0.1-0.2 Large intestine = 0.5-1.0 Rectum = 0.04-0.07
46
describe multiple absorptive mechanisms of intestines
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
can all drugs be delivered orally?
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
define bioavailability
fraction of drug administered reaching systemic circulation
49
what is significance of bioavailability
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
what affects bioavailability
Route of administration
51
describe intravenous effect on bioavailability
bypass liver High initial concentration in blood fall quickly - goes to liver and into tissues
52
describe intramuscular effect on bioavailability
time lag from absorption into muscle Peak not as high Does not go to liver first
53
describe sublingual effect on bioavailability
not as fast as muscle but still good No first pass
54
describe oral effect on bioavailability
Lowest First pass
55
define distribution
Transfer of drug from blood stream to other sites where they need to go
56
describe drug - distribution
Free drug in extracellular fluids All things happen = bound, broken down and gets to specific sites of drug action
57
Distribution of IV anesthetic
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
describe halothane redistribution
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
how does free drug get distributed
Free drug has to get out of circulation and be distributed into body variety of places
60
where can free drug go
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
describe drug fate in tissues - general
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
describe drug fate in tissues - metabolism
Some drugs metabolized by cells Like liver cells Drug metabolites can also go out into circulation
63
describe drug fate in tissues - free drug
Free drugs that are lipid soluble can cross membranes Can be transported and can bind and metabolites can occur in other tissues
64
how can drugs pass
diffusion or facilitated diffusion (passive) or by active transport
65
describe Properties affecting tissues permeability
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
describe peripheral capillary - what can pass through
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
what can alter drug distribution
Disease can alter drug distribution Cancer = tumour alter properties of blood vessels that supply tumour Can make drugs have less access or greater
68
what is ideal for administering drug
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
what do Variables affecting drug concentration alters
rate and height
70
describe variables affecting drug concentration
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
describe blood brain barrier
Capillaries in brain have no spaces between endothelial cells
72
describe blood brain barrier features
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
blood brain barrier length
Human brain capillaries = 400 miles, very complex
74
when can Blood brain barrier can be impaired
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
what else protects brain
Also have blood cerebrospinal fluid barrier
76
Where is csf made
Cerebrospinal fluid made in choroid plexus - also monitors what gets into csf
77
describe csf and brain pathway - get in
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
describe csf and brain pathway - get out
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
name a special tissue we need to consider effect of drugs on
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
describe protein binding in circulation
If bound = cannot get out Mainly albumin bound to drug Some glycoproteins
81
describe protein bound fraction
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
can proteins in circulation be altered
Proteins in circulation can be altered
83
give examples of when proteins in circulation altered
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
name models of distribution
one compartment two compartment
85
describe one compartment model of distribution
Distribute equally everywhere Reality is More complex than this
86
describe two compartment model of distribution
Immediately after administration = concentration of drug higher in tissues with more blood flow Brain, lungs, heart, liver After distribution = equilibrium everywhere
87
describe p glycoprotein
transports drugs out of cell Very effective Ex = drug can cross membrane (soluble) but p ejects from cell immediately Hard sometimes = for cancer
88
compare distribution vs elimination
Distribution = Sharp decline at beginning = blood being redistributed out of blood Elimination = Slow decline as blood continuously flows through liver
89
describe volume of distribution
where does it go Peripheral volume = everything else Central volume = blood Over time drug will get distributed Volume of distribution = Vd
90
describe Vd
Amount of drug in body / concentration in plasma Amount = what you gave
91
what are variations in Vd due to
Properties of drug Protein binding =How much bound in circulation Tissue binding = How much bound in tissue
92
what is avd
Apparent volume of distribution = AVD APPARENT RATHER THAN ACTUAL VOLUME
93
Calculations for Vd
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
when is avd small
If drug mainly found in circulation= avd small = mostly still in blood High protein binding = high concentration in blood = low avd
95
when is avd large
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
what can we use to calculate loading dose
avd - tissue binding vs protein binding
97
what is loading dose
How much drug you have to give to get certain amount in concentration
98
describe volume of distribution - gen
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 (22 decks)

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