Pharmacokinetics

Question 1

4 main parts to pharmacokinetics

Answer 1

Absorption, distribution, metabolism, elimination

Question 2

absorption

Answer 2

the proportion of an administered drug that reaches systemic circulation- bioavailability

Question 3

what affect absorption (3)

Answer 3

GI, Route of admin and lipophilicity

Question 4

GI AND ABSORPTION

Answer 4

contains proteases which may breakdown the drug, monoclonal antibodies- breakdown and recombinant proteins

• first pass metabolism - since hepatic vein takes blood from the stomach to the kidney

Question 5

route of administration and absorption

Answer 5

IV= direct= 100% bioavailaiblity
Oral- via GI- we’ll tolerated but lower bioavailiablity
IM- slower, via capillary
Respiratory- across plasma men- rapid

Question 6

drugs have to be

Answer 6

lipid soluble to pass membrane - therefor NOT IONISED

Question 7

weak acids have

Answer 7

a low Ka, but a high pKA- pH at which 50% of the drug is ionised and 50% is nonionised

Question 8

Distribution is referred to as

Answer 8

the volume of distribution

Question 9

the volume of distribution

Answer 9

Vd

Question 10

what is Vd

Answer 10

process by which drug is transferred from the blood to the tissue
- after absorption the drug equilibrates between the plasma and tissue

Question 11

more detailed definition of Vd

Answer 11

‘vd represents the volume in which total amount of drug would need to be dissolved to match plasma conc’

Question 12

what affects Vd

Answer 12

• drug size
• lipophilicity
• body composition

Question 13

Vd=

Answer 13

Dosage/ conc of drug in plasma

Question 14

Vd unit

Answer 14

mL

Question 15

High plasma conc=

Answer 15

low Vd- drug not widely distributed

Question 16

Low plasma conc=

Answer 16

high Vd - drug widely distributed

Question 17

metabolism occurs in

Answer 17

the cell e.g. prodrug and in the liver = first pass metabolism

Question 18

first pass metabolism

Answer 18

reduces bioavailability

• most drugs are metabolised slightly but the gut or the liver
• occurs in the LIVER and deactivates drugs

Question 19

if first pass metabolism occurs

Answer 19

higher dose may occur

Question 20

bioavailability is 100% if given via

Answer 20

IV

Question 21

hepatic clearance

Answer 21

metabolism by the liver

Question 22

renal clearance

Answer 22

exertion by the kidney

Question 23

zero order drugs

Answer 23

constant AMOUNT of drug cleared per unit of time

Question 24

first order drugs

Answer 24

constant PROPORTION of drug cleared per unit time

Question 25

most drugs are

Answer 25

FIRST ORDER

Question 26

what does zero order graph look like

Answer 26

straight decrease over time

Question 27

what does first order graph look like

Answer 27

exponential decrease over time

Question 28

2nd order drugs

Answer 28

4x rate of clearance

Question 29

3rd order drugs

Answer 29

8 x rate of clearance

Question 30

how is renal clearance measured

Answer 30

experimentally following IV admin of known out of drug

Question 31

Renal clearance =

Answer 31

[drug] in urine time flow rate/ [drug] conc in plasma

Question 32

factors effecting renal clearance

Answer 32

• renal blood flow

- drug lipophilicity

Question 33

which drugs are most easily reabsorbed in the kidneys

Answer 33

WEAK ACIDS since they are more lipid soluble- have a lower Ka and higher pKa

Question 34

low pH in urine=

Answer 34

less excretion

Question 35

plasma half life

Answer 35

the time in which plasma conc reaches by half

Question 36

plasma half life for first order

Answer 36

exponential decrease

Question 37

plasma half life for zero order

Answer 37

increased - straight line

Question 38

how to measure plasma half life

Answer 38

measured experimentally following IV admin of known amount t of drug

Question 39

a drug with a short half life

Answer 39

may require regular repeats

Question 40

drug targeting is good because

Answer 40

1) reduces side effect
2) increases bioavailability
3) more predictable response
4) less of the drug needed

Question 41

targeting drugs exploits

Answer 41

property of target tissue e.g. pH

Question 42

IC50

Answer 42

conc of antagonist that reduces the biological effect of an agonist by 50%