ADME 3 Flashcards

1
Q

what must drugs be in in order to be absorbed?

A

in solution-i.e dissolved

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2
Q

how do most drugs cross membranes?

A

passive diffusion

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3
Q

what membranes are lipophilic?

A

–rate-limiting to onset
–stomach wall–
cell membranes–
blood-brain barrier

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4
Q

what 2 compounds are actively transported?

A

a-amino acids

sugars

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5
Q

how does a drug behave with two immiscible liquids?

A

Equilibrium is set up between the two phases depending on the relative affinity for each

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6
Q

what is the equation for the partition coefficient (P)?

A

conc of drug organic/ conc of drug aqueous

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7
Q

what does a high partition coefficient imply?

A

highly lipophilic drug

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8
Q

low is P also written?

A

Log P , Log10P

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9
Q

How do you measure the partition coefficient?

A

shake flask
HPLC
electrochemical

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10
Q

if the Log P is less than 1 what does it imply?

A

favours the organic side

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11
Q

what kind of modeling does the partition coefficient allow for?

A

quantitative modeling- how readily does a drug partition between the two media

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12
Q

does the partition coefficient apply to ionised or unionised drugs?

A

unionised

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13
Q

what is the shake flask method?

A
  • Drug is allowed to equilibrate between two immiscible liquids
  • Layers are separated and the concentrationin both layers is determined
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14
Q

how do you partition ionisable drugs?

A

All ionised drug will reside in the aqueous layer
Unionised drug will equilibrate
between organic and aqueous layers

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15
Q

what is P app?

A

Apparent partition coefficient at a particular pH•pH dependent –degree of ionisation will change with pH

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16
Q

what is P true?

A

partition coefficient of the unionised form of the drug

17
Q

what is the rages of P app?

A

0-P true

18
Q

what are the ranges of Fu?

A

0-1

19
Q

what is the formula for Papp?

A

pAPP=p truex fu

20
Q

does the formula for papp apply to partially ionised bases?

A

yes

21
Q

what are weak bases most lipophilic in?

A

acidic environments

22
Q

what are weak bases most lipophilic in?

A

alkaline environments

23
Q

why is it difficult to measure p true expermentally?

A

as almost no drug would be left in aq environment

24
Q

for weak acids what does p app decrease with

A

increasing ph-Drug becomes more water soluble with increasing pH as it becomes more ionise