Topic 3 - Potency and Selectivity

Question 1

What is ED50

Answer 1

Effective dose that gives 50% of maximum therapeutic effects

Question 2

How does Kd effect potency

Answer 2

The lower Kd = Less drug required to reach 50% = More potent drug

Question 3

What increases Potency of Agonist

Answer 3

Agonist Efficacy
Binding Affinity

Question 4

What increases Potency of Antagonist

Answer 4

Binding Affinity

Question 5

What is efficacy

Answer 5

Ability of agonist to stimulate a receptor

High efficacy means agonist produces a large effect

Question 6

How does efficacy affect Kd

Answer 6

Efficacy is more related to the physical effects from receptor binding

Kd only focuses on receptors bound, thus, the two are not related

Question 7

How does efficacy affect potency

Answer 7

Potency refers to the magnitude of the response produced by an agonist

High efficacy will likely produce a larger response, meaning a lower concentration of drug is needed
(Lower Dose to achieve ED50 = Higher Efficacy = More Potent)

Question 8

Selectivity (Effects of a Low Dose)

Answer 8

A drug will preferentially bind to different receptors
Lower Kd / better shape fit for a receptor = More preferred

Thus, at low enough doses a drug will only bind to what it prefers

Question 9

Selectivity (Effects of a High Dose)

Answer 9

When concentration of drug is too large it can start to impact off target receptors leading to side effects

Drug starts binding to receptors that it normally does not prefer