drug passes through the cell- fist the membrane then the cyto then back out
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Paracellular pathway
drug passes inbetween cells - ie they are leaky - transdermal drugs rely on this transport pathway
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what are lipinkskis rules
no more than 5 h. bond donors. No more than 10 h bond acceptors. MW<500. logP < 5
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an oral drug according to Lipinksi can violate how many of these criteria?
only 1
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Tight Junctions
form between cells - prevent free mvt
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what type of molecules have higher solubility
charged/polar/ionized molecules
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what type of molecules are best absorbed through the membranes
un charged/ non ionised/ lipophilic
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What are the best types of drugs
ones which have both some water and lipid solubility
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what would happen if the drug was very insoluble
would not dissolve - no therpautic effect since x be absorbed- excreted chemically unchanged in the urine
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how can we increase solubility (4)
1. reduce particle size, 2. change the pH, 3. form a salt/ester, 4. create and amorphous solid
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why do charged molecules have higher solubility in water?
due to their ability to form ion-dipole interactions in water which are stronger than the other types of IMF
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what is partitioning?
the ability of a substance to position itself in 2 layers of immiscible liquids- octanol + water are often used
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how to work out P for non ionisable drugs
p= [drug]oct/[drug]water
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how to work out P for ionisable drugs
[drug]oct/[drug]water+[drug ion]water
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what does it mean if logP =0
that there is equal distribution in both liquids since log1 =0
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what does it mean if logp >0
the drug is lipid soluble
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what does it mean if logp <0
the drug is water soluble
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ideal logP value for drugs
1-2 , we want it to have both water solubility and lipid solubility to max both dissolution and absorption
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what is the pH partition theory
if we have an ionizable drug - it will be absorbed in its non ionised form - then once absorbed into the blood then it will dissociate back to form the ionised active form of the drug - ie lidocaine
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what does the pH partition theory assume?
drug passes through the membrane via passive diffusion
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2 types of solid are
crytsaline and amorphous
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crytsaline
ordered, structured in arrangement .
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Amorphous
means without form - randomly orientated- no order
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types of crytaline solid
polymorphs 1,2,3 - they each differ by their MP, solubility, stability, dissolution rate etc
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how to determine between crystaline and amorphous?
using power Xray diffraction
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crystaline produces
sharp defines brag lines
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amorphous produces
shorter less sharp brag lines
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what type of molecules are most susceptible to hydrolytic degradation
amides, esters , B lactams (penicillin)
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How can we prevent degradation via hydrolysis (2)
1. moisture preventing packaging 2. suspend in non aq solvent ie. alchol/glycerin
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molecules most susceptible to oxidation
Phenols, heterlytic compounds
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Other cards in this set
Card 2
Front
Paracellular pathway
Back
drug passes inbetween cells - ie they are leaky - transdermal drugs rely on this transport pathway
Card 3
Front
what are lipinkskis rules
Back
Card 4
Front
an oral drug according to Lipinksi can violate how many of these criteria?
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