D in ADME

Question 1

what are the general assumptions we make with pharmacokinetic models?

Answer 1

drug is absorbed instantly
some drugs may not distribute uniformly
drug is eliminated uniformly
there’s one compartment model
- plasma conc. is true for the entire circulation

Question 2

what can happen after IV bolus administration?

Answer 2

-distribute quickly in well perfused organs/tissue = rapid equilibrium
-distribute slowly to poorly perfused organs/tissue = slow equilibrium

Question 3

what are the compartments in two compartment model?

Answer 3

central compartment
peripheral compartment

Question 4

what is the central compartment ?

Answer 4

systemic blood circulation

Question 5

what are the compartments in one compartment model?

Answer 5

central compartment

Question 6

what is the distribution phase in the two compartment model?

Answer 6

where the drug is moving from the central compartment to the peripheral compartment

Question 7

what is the elimination phase in the two compartment model?

Answer 7

predominant process during the second phase of the biphasic plot

Question 8

what is the main mechanism of defence of the blood brain barrier?

Answer 8

efflux transporters

Question 9

how can we use drugs to pass the BBB?

Answer 9

using pro-drugs

Question 10

what is the blood-cerebrospinal fluid barrier?

Answer 10

barrier between the BBB and the CSF

Question 11

how can we bypass the blood-cerebrospinal fluid barrier?

Answer 11

using intrathecal injections

Question 12

what characteristics will increase diffusion pass the placental barrier?

Answer 12

MW <600Da
lipophilic drugs
unionised
Lower than blood pH compared to in adults

Question 13

what are the processes drugs can enter the placenta?

Answer 13

endocytosis
active transport
facilitated transport
passive diffusion

Question 14

why can drugs pass the placenta?

Answer 14

as the apical and basal membrane thickness decreases during pregnancy to allow nutrition to be exchanged, however, also allowing drugs to pass thru

Question 15

whats plasma?

Answer 15

the liquid phase of the blood, composed of water and proteins

Question 16

what cells does the blood contain?

Answer 16

RBS (erythrocytes)
platelets (thrombocytes)
WBC (leucocytes)

Question 16

if a drug binds to the following
RBS (erythrocytes)
platelets (thrombocytes)
WBC (leucocytes)
what does this mean?

Answer 16

the drugs blood concentration and the drugs plasma concentration will be the same
forming an equilibrium

Question 17

how do you work out the blood:plasma ratio?

Answer 17

Question 18

how do you work out the drug blood partition coefficient?

Answer 18

Question 19

what does it mean if the blood:plasma ratio = 1?

Answer 19

no issues with the PK

Question 20

what happens if you’re value of how do you work out the blood:plasma ratio is <1/>1?

Answer 20

there is a difference in the PK parameters in the blood vs plasma

you must state the time taken of the blood sample