pharmocokinetics

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  • Created by: Louisa
  • Created on: 26-09-20 11:52
what are four main principles to pharmokinetics (ADME)
absorption of the drug, distribution of the drug molecules, metabolicm of the parent drug, excretion or elimination of the drug and its metabolites
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all processes are often
dynamic and simultaneous
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what physiological factors affect absioption
blood flow, SA, contact time at active site, age of Pt, gi contents, gi pH
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what physiochemical factors affect absorption
solubility, chemical stability, particle size, lipophilicity, pka
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Absorption mechanism (5) differnt ways
passive diffusion, carrier mediated diffusion (active trasnport) ion and electrochemical diffusion (permeability), ion-pair transport, endocytosis
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how is passive diffusion calculated (what law)
Ficks law
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what is ficks law
R= (high conc. - low conc.) * (SA * K permability constant) / membrane thickness
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What is the pKa of a drug
how acidic it is
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where the pKA and pH are equal
50% of the drug is ionized and 50% of the drug is unionzed
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drugs that are uncharged are more
lipophilic and hydophobic, so are more likely to pass through the cell mambrane
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what is bioavalibility
the proportion of the drug which enters the circualtion when introduced into the body and so takes an active effect
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what drug has 100% bioavlibility
Iv
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what does distribution refer to
the reversible movement of a drug from the blood and tissues and th erelative proportions of the drug within the tissues
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plasma protein binding refers to the drugs
binding to plasma proteins, blood cells and extracelluar tissue proteins
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the extent of the binding affects the avlibility of the drug for
therapeutic effect
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binding mkaes the drug
inert
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binding affects it by changing the
absorption, metabolism and excretion
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can binding be reversible or irreversible
both
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when binding is reversible
weaker bonds, equilibrium and lipoproteins
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when is binding irreversible
storng bonds = which leads to drug toxicity
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blood brain barrier is made up of
endothelial cells joined by tight junctions
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are drugs easily able to acess the brain
no
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can drugs cross the plcental barrier
yes easily
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crossing the placental barrier measn what for the baby
can cause malformations to the foetus
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what is metabolism
it aims to turn drugs more poalr and more water soluble
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what factors affect metabolism
liver disease, genetic difference, enzymes inhibition, tolerance, age, alcohol consumptino, smoking
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what is the first pass effect
the rapid uptake and biotransformation of a drug into a non-active metabolite
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what is a half life also known as
duration of action
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a half time is defined as
time for drug concentration to decrease by half i nthe body
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the half life can vary depending on
individual physiologyical factors
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what is volume distribution
the total amount of a drug i nthe body/ blood plasma conc.
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it is a theoretical concept meaning
doesn;t correspond to the actual amount
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a high volume of distribution means the drug is concentrated where ...or is...
conc intracelluarly, leaving a low plasma conc, or is trapped in aother body compartment
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a high volume of distribution means the drug is restricted to
a particualr compartment, extracellular fluid or plasma
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how many phases are there to biotrasnformation
phase 1 and phase 11
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what chemical reaction at phase 1
oxidation, reduction or hydrolysis of a drug
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this chemical reaction causes the products to be
more chemically reactive
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what is the common oxidation
cytochrome p450 enzymes
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what does the cytochrome p450 enzymes do
make drug inactive or active
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phase 11 of the biotrasnformation adds what improving
adds a polar group inproving solubility making it less biologically active
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what is a prodrugs
a pharmacologically inactive drug
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metabolism is the
inactive form of a drug
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why would we use a prodrug
to overcome dificulties such as poor solubility or chemical instability
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excretion refers to the
elimation of the drug
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renal elimination involes
active glomerular filtration and postive diffusion into renal tubules
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renal excretion extent depends on
glomerulr filtration, tubular reabsorption and tubular secretion
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excretion by the liver
into bile to gut for feacal elimination
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excretion via saliva and sweat is a
minor route
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enterohepatic cycling refers to the drug being
cycled aorunf the liver and intestine = prolonged half life
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intestinal bacteria =
hydrolyse to oringal drug
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clearance (cl) refers to
drug elimation
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clearance is defined as
volume of bodily fluid from which the drug is removed per unit of time (ml/min)
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amount of the drug removed changes as the
blood conc. changes.
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Other cards in this set

Card 2

Front

all processes are often

Back

dynamic and simultaneous

Card 3

Front

what physiological factors affect absioption

Back

Preview of the front of card 3

Card 4

Front

what physiochemical factors affect absorption

Back

Preview of the front of card 4

Card 5

Front

Absorption mechanism (5) differnt ways

Back

Preview of the front of card 5
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