drug absorption and distribution

Question 1

3 factors to consider in drug absorbtion

Answer 1

1. drug properties
2. patient factors
3. possible routes of admin

Question 2

4 mechanisms of drug absorption (cellular)

Answer 2

1. passive diffusion
2. facilitated diffusion
3. active transport
4. phagocytosis

Question 3

3 properties of drugs that affect absorption

Answer 3

1. chem structure size etc.
2. lipid and water solubility
3. ionization

Question 4

what is usual molecualr weight of drugs

Answer 4

250-450 Da

Question 5

at what size can a lipid soluble drug diffuse across membrane

Answer 5

1000Da

Question 6

what is partition coefficient

Answer 6

[drug in membrane]/[drug in buffer]

Question 7

what does higher partition coeff. mean

Answer 7

more lipid soluble

Question 8

what increase and decrease PC

Answer 8

incr- hydrophobic groups (benzene, CH3)

dec. - hydrophilic groups - OH, COOH,

Question 9

what is the effect of drug ionization

Answer 9

uncharged form is generally easier to cross membrane

Question 10

** what happens with higher Ka in acid and basic drug - when increase pH over pKa

Answer 10

acid - more ions

basic - less ions

Question 11

what are drug transporters

Answer 11

proteins responsible for moving drugs into and out of cells

Question 12

most common locations of transporters

Answer 12

apical layer of hepatocytes, enterocytes, tubular cells

Question 13

2 main classes of drug tranporters

Answer 13

1. uptake transporters

2. efflux transporters

Question 14

why are transporters relevant

Answer 14

1. also affects distribution and elimination

2. need to know if drug is a substrate, inhibitor, or inducer of transport

Question 15

what is volume of distribution

Answer 15

volume of total body fluid that is absorbing the drug

Question 16

4 drug properties that influence distribution

Answer 16

1. size and structure
2. lipid solubility
3. degree of ionization
4. protein binding

Question 17

3 other factors affecting distribution

Answer 17

1. blood flow
2. cap. permiability
3. barriers

Question 18

what are the 3 body compartments and avergae size for 70kg male

Answer 18

1. water - 42L
2. fat - 14L
3. bone - 5L

Question 19

what is apparent vol. of distribution

Answer 19

hypothetical vol. into which drug is disseminated

Question 20

when is apparent vol used

Answer 20

when want to compare withing different compartments of body

Question 21

formula for Vd

Answer 21

total drug in body/intial plasma [c]

Question 22

what does app Vd tell us

Answer 22

an idea if the drug is beyond the plasma

Question 23

when does knowing Vd help

Answer 23

1. idea of where drug might be distributed
2. when predicting plasma [C]
3. determining dose of drug to produce desired plamsa [C]
4. deciding whether to dyalize when poisoned