L3 - principles of drug action 1 - conc response relationship

Question 1

what shape is a log[drug] - response curve

Answer 1

sigmoidal

Question 2

what shape is a [drug] response curve

Answer 2

hyperbola

Question 3

what are the 3 main experiment types

Answer 3

1. in vitro
2. in vivo
3. ex vivo

Question 4

what is in vitro and give example

Answer 4

drug effects studied on tissue dissected and kept alive outside the body

eg cells grown in tissue media

Question 5

what is in vivo and give example

Answer 5

drug effectiveness tested on living organism

eg clinical trials/animal models

Question 6

what is ex vivo and give example

Answer 6

animal is treated with drug, killed, then target organs removed and tested in vitro

eg does long term treatment of drug cause liver damage to mice

Question 7

what is a cumulative conc response curve (in vitro)

Answer 7

drug isnt washed out after each added concentration

Question 8

why can M conc not be used in vivo? what conc is used

Answer 8

because the volume of solvent (blood) varies and isnt always known

weight of drug per weight of animal

Question 9

define Emax

Answer 9

max effect a drug can produce

Question 10

define EC50

Answer 10

(molar) conc of drug that produces half of max effect

Question 11

what does potency mean?

Answer 11

describes the conc at which a drug is effective

potent drug is more effective at lower concs

Question 12

what does a lower EC50 mean in relation to potency?

Answer 12

more potent

Question 13

what is potency ratio?

Answer 13

a way of calculating relative potencies of 2 drugs using their EC50

Question 14

define bioassay

Answer 14

any techniques where drug potency is determined by measuring biological response

Question 15

what is 2+2 bioassay - how is it carried out

Answer 15

1. draw log[conc] - response curve for the two drugs

2. measure the difference between the two lines at a low and high conc - this should be the same and is logM

Question 16

define therapeutic index

Answer 16

ratio between toxic dose of drug and the dose producing the desired effect

Question 17

what does higher therapeutic index mean

Answer 17

less chance of toxic side effects

bigger difference between toxic and therapeutic dose

Question 18

how is therapeutic index calculated

Answer 18

ED50 (effective dose in 50% population)

Question 19

is ED50 always the same for a drug?

Answer 19

no

the ED50 for ibuprofen treating headache will be different to the ED50 for ibuprofen treating arthritis

Question 20

why does the therapeutic index still need to be treated with caution?

Answer 20

because there are large variations in TD and ED between people