11. theories of drug action

Question 1

Answer 1

Question 2

common characteristics of receptors

Answer 2

1. act as molecular switches (active/ inactive)
2. amplification

Question 3

type of drug on enzymes, transporters, ion channels

receptors

Answer 3

inhibitors

2 types- agonist/ antagonist

Question 4

affinity

Answer 4

ability of drug to bind to its receptor

Question 5

efficacy

Answer 5

The ability of a drug, once bound, to activate the receptor by a conformational change

Question 6

agonist

antagonist

Answer 6

has both affinity and efficacy

only affinity

Question 7

which law does drug action obey

association rate constant

dissociation rate constant

at equilibrium

Answer 7

law of mass action

binding proportional to conc

Kon= [D][R]

Koff= [DR]

Kon[D][R]= Koff [DR]

Kd= [D][R]/[DR]

Question 8

Kd

Answer 8

concentration of drug needed to occupy 50% of receptors i.e. a measure of its binding affinity

Question 9

potency

Answer 9

EC50 - Effective Concentration of agonist for 50 % of its maximal response. A measure of agonist potency

= conc dependence of the effect (not how big the effect)

Question 10

Answer 10

Salmeterol is 100 fold more potent than adrenaline in this assay (EC50).

Salmeterol is a partial agonist compared to adrenaline for airway relaxation (Rmax) – it has lower efficacy (ability to activate the receptor)

Question 11

EC50 and Rmax values determined by….

conc response curve

Answer 11

(i) Drug-receptor interaction: agonist affinity and efficacy

and (ii) Properties of the functional response – e.g. amplification