intro to pharmacokinetics (drug distribution) Flashcards
what determines ADME
structure of a drug molecule
what may be needed for a drug to provide a response
prolonged exposure of the target with the drug
by repeated dosing
best way for drugs to get to targets
through blood
how much of every person is water
70%
what do some drugs bind to in the blood
plasma proteins
do drugs bound to plasma proteins have clinical effect
no, only free drugs do
is there equilibrium in the drug between those bound to plasma protein and those that are free
yes
what happens with drugs not bound to plasma protein
more of the drug can leave to
- go to the target
- be metabolised
- be excreted
drugs bound have much less concentration leaving to do those things
do free drugs or drugs bound to plasma proteins stay around for longer
drugs bound to plasma proteins stay around for longer
how do drugs leave the circulatory system
through pores
is there many pores in CNS
no, makes it harder for drugs to leave
once the drug enters the cell can they still bind to other things
yes, can bind to mitochondria etc
what is in the central compartment (two compartment model)
water and proteins
what does the drug do in the central compartment
equilibrates between free and bound drug
only free drug in the water can get to targets
what is the second compartment made up of (two compartment model)
proteins and lipids
water
what happens to the drug in the second compartment
equilibrate between free and bound drugs
what happens to drugs with high plasma protein affinity
they stay in the blood
what happens to drug with high tissue protein affinity
it all goes to the tissues
what volume is the water compartment
0.07L/kg
how is drug distribution measured
measure of how distributed drug is between blood and tissue
Vd of blood
0.06L/kg
what does it mean is Vd of drug is 0.06L/Kg
drug stays in the blood
what does it mean if drug has a Vd of 0.25L/kg
the drug stays in water, blood and extra vascular fluid
can’t get into cell
what does it mean is Vd of drug is 0.07L/Kg
the drug stays in the cells, blood and water
what does it mean if Vd is less than 0.7L/Kg
the drug must leave the water and go into the tissues
means very little free drug in water as its all in tissues and you must give more drug to get to target
what does Vd of less than 0.7l/kg mean in terms of half life
it is greater and it can’t be excreted as its all in tissues
do drugs that are lipophilic have low of high Vd
high
do drugs that are hydrophilic have low of high Vd
low as can’t get into cells easily
are acidic drugs highly plasma bound or free drugs
highly plasma bound as they are attracted to albumin (plasma protein)
what are basic drugs attracted to
tissues
do acidic or basic drugs have a higher Vd
basic have higher Vd compared to acids
can drugs with high Vd be removed via haemodialysis
no
why does high Vd vary from person to person
high fat content etc
high fat means drug enters adipose tissues
low fat means all drugs go to tissues
