Lecture 5 Drug receptor theory (antagonists)

Question 1

What is chemical antagonism

Answer 1

antagonism chemically alters the agonist so the effects of active drug is lost

Question 2

What is pharmacokinetic antagonism

Answer 2

antagonism controls the concentration of drug in the body through ADME (absorption, distribution, metabolism, excretion)

Question 3

what is physiological antagonism

Answer 3

two drugs that exert opposing action in particular tissue or system

Question 4

what is non-competitive antagonism

Answer 4

blocks a step in the process between receptor activation and response

Question 5

competitive antagonists

Answer 5

bind to same site as the agonist and stabilises the receptor so it cannot be activated. these can be reversible or irreversible.

Question 6

how does reversible competitive antagonism effect concentration-response curve?

Answer 6

causes a parallel rightward shift in the concentration-response curve and no change in the maximum response.

Question 7

how does concentration of reversible competitive antagonist effect the shift in concentration-response curve

Answer 7

the higher the concentration of the antagonist, the further the shift to the right. EC50 also increases.

Question 8

what is a dose ratio?

Answer 8

how many more times the agonist is needed in the presence of an antagonist

Question 9

how does an irreversible competitive antagonist effect a concentration-response curve?

Answer 9

this cannot be reversed and is time dependant.
does not reach equilibrium so KD cannot be calculated by schild analysis.
as the concentration is increases, the maximum is decreased.

Question 10

how to get rid of irreversible antagonism

Answer 10

have to wait for antagonist drug to be secreted and new receptors to be made.

Question 11

what does schild plot analyis measure?

Answer 11

measures the competitive antagonist affinity

Question 12

what is the schild equation ?

Answer 12

pA2 = - log10 (molar concentration of antagonist that gives a dose ration of 2)

Question 13

rearranged schild equation

Answer 13

KD = inverse log (-1*pA2). if a drug has pA2 value =6, KD value will be 1x10-6 M

Question 14

how does a partial agonist effect a concentration-response curve?

Answer 14

causes a shift to the right.
initial response increases as partial agonist concentration increases.
when full agonist is added with partial agonist the curve shifts to the right