L3-4 PHRM20001 Agonists & Antagonists

Question 1

When Kd = D, __% receptors bound

Answer 1

50

Question 2

in vitro, in vivo, which one is dose = conc

Answer 2

In vitro

Question 3

EC50 and PEC50 are measures of___

Answer 3

Drug potency NOT affinity. EC50 does not equal KA

Question 4

EC50 and IC50

Answer 4

EC50 is the concentration of a drug that gives half-maximal response. The IC50 is the concentration of an inhibitor where the response (or binding) is reduced by half.

Question 5

Potency

Answer 5

How much drug is need for effect

Question 6

Efficacy

Answer 6

Ability of a drug to activate the receptor. Looks at amount of response that can be elicited.

Question 7

Antagonists have no efficacy in ____ and is active in ___ if ___ is present and hence have clinical efficacy with a measurable potency

Answer 7

Vitro, vivo, agonist

Question 8

1) Competitive/Surmountable
2) Insurmountable
3) Non-comp. functional antagonism

Answer 8

1) Parallel, rightward shift, max unchanged - however not all competitive antagonists are surmountable
2) Not parallel, rightward shift, max decreased
3) 2 drugs with opposing actions in the same cell

Question 9

Gaddums equation

Answer 9

[AR]/[R]Total = [A]/ [A] + KA (1 + [B]/KB)

Question 10

pA2

Answer 10

approxes pKB, it is the -ve log of the conc of antagonist required to cause a two-fold rightwards shift of agonist conc-response curve.

Question 11

Schild plot

Answer 11

Plot of the relative shift of the agonist curve against antagonist conc. A linear plot with a slope of 1 indicates a competitive antagonist.

Question 12

pKB vs pA2

Answer 12

pKB is antagonist affinity, pA2 is antagonist potency. pKB = pA2 when the slope =1

Question 13

Benzodiazepines

Answer 13

Increases the affinity of the receptor for GABA

Question 14

Atropine

Answer 14

Muscarinic Cholinoreceptor competitive antagonist

Question 15

Mepyaramine

Answer 15

Competitive anithistamine