ADME 3 Flashcards
what must drugs be in in order to be absorbed?
in solution-i.e dissolved
how do most drugs cross membranes?
passive diffusion
what membranes are lipophilic?
–rate-limiting to onset
–stomach wall–
cell membranes–
blood-brain barrier
what 2 compounds are actively transported?
a-amino acids
sugars
how does a drug behave with two immiscible liquids?
Equilibrium is set up between the two phases depending on the relative affinity for each
what is the equation for the partition coefficient (P)?
conc of drug organic/ conc of drug aqueous
what does a high partition coefficient imply?
highly lipophilic drug
low is P also written?
Log P , Log10P
How do you measure the partition coefficient?
shake flask
HPLC
electrochemical
if the Log P is less than 1 what does it imply?
favours the organic side
what kind of modeling does the partition coefficient allow for?
quantitative modeling- how readily does a drug partition between the two media
does the partition coefficient apply to ionised or unionised drugs?
unionised
what is the shake flask method?
- Drug is allowed to equilibrate between two immiscible liquids
- Layers are separated and the concentrationin both layers is determined
how do you partition ionisable drugs?
All ionised drug will reside in the aqueous layer
Unionised drug will equilibrate
between organic and aqueous layers
what is P app?
Apparent partition coefficient at a particular pH•pH dependent –degree of ionisation will change with pH