ADME 2

Question 1

what are the two routes to absorption?

Answer 1

transcellular and paracellular

Question 2

what percentage of cardiac output supplies the GI tract?

Answer 2

10%

Question 3

what is paracellular absorption also known as?

Answer 3

connective absorption

Question 4

what sizes do molecules have to be in order to pass through the paracellular route?

Answer 4

radius less than 4 armstrongs

Question 5

which way does passive diffusion move through a conc gradient?

Answer 5

down a conc gradient

Question 6

what’s a problem with injecting phenytoin?

Answer 6

crystallisation in muscle tissue due to difference in PH

Question 7

what is the problem with taking phenytoin orally?

Answer 7

poor absorption from the stomach- bad at low ph

absorption is irregular

Question 8

is passive diffusion specific or non-specific?

Answer 8

non-specific, anything lipid soluble(most drugs)

Question 9

what is facilitated diffusion?

Answer 9

Movement of drug across a cell membrane via a specialised transport system embedded in the cell membrane

• occurs without energy
• no conc gradient

Question 10

where does active transport get its energy from?

Answer 10

from the hydrolysis of ADP to ATP

Question 11

what system provides 1/3 of the energy we use?

Answer 11

na+/k+ ATPase channel

controls signals through the brain and water flow in cells

Question 12

for passive diffusion are the species usually charged or non-charged?

Answer 12

non-charged

Question 13

what is a requirement of passive diffusion?

Answer 13

must be in solution

Question 14

what kind of equilibrium does passive diffusion have?

Answer 14

dynamic

Question 15

what are the 6 requirements for passive diffusion?

Answer 15

1-water solubility
2- lipid solubility
3-molecule must be unionised
4-Molecular size
5-Concentration at site of absorption
6-Surface area of site of absorption

Question 16

what do ionised compounds form?

Answer 16

complexes with endogenous ions resulting in an neutral species overall

Question 17

what is lipinski’s rule of 5?

Answer 17

• Not more than 5 hydrogen bond donors
• Not more than 10 hydrogen bond acceptors(nitrogen or oxygen atoms)
• A molecular weight under 500 daltons(amu)
• A partition coefficient (log P) less than 5

Question 18

what is the ph partition hypothesis?

Answer 18

When pH on one side of a membrane differs from the pH on the other side, then if the drug is either an acid or a base, the drug will be ionised to different extents on each side of the membrane

Question 19

what happens in sink conditions?

Answer 19

Absorbed drug is removed by bloodstream•
Equilibrium is never established•
(High) concentration gradient is maintained

Question 20

how much of a weak acid is ionised at ph=pka+2

Answer 20

99%

Question 21

how much of a weak base is ionised at ph=pka+2

Answer 21

1%

Question 22

what is the equation for the fraction of drug ionised?

Answer 22

1/1+antilog <10(ph-pka)