PHL 211 Pharmacology
Third Lecture
By
Abdelkader Ashour, Ph.D.
Phone: 4677212
Email: [email protected]
Dose-Response Functions
Biological Effect
Displays the relationship between the dose of a ligand and some
biological response to that ligand
20
30
40
Dose-Response Functions, contd.
 Efficacy (Emax)
The maximal response that the drug can produce. It is the effect that is
observed at saturating concentrations
 Agonists will have high efficacy, whereas antagonists will, generally, have zero efficacy
 EC50 (ED50)
The concentration or dose of the drug that is needed to produce a 50%
maximal response
100 -
(A)
75 -
50 ----------------------------
Red
(B)
----------25 -
1
50
100
Log Dose (mg)
Which drug has more efficacy? And why?
Dose-Response Functions, contd.
 Potency
The amount (weight) of drug in relation to its effect.
For example, if the weight-for-weight drug X has a greater effect than drug Z 
drug X is more potent than drug Z, although the maximum therapeutic effect may
be similar with both drugs
 Drugs of high potency will generally have a high affinity for the receptors and
thus occupy a significant proportion of the receptors even at low
concentrations
100 -
(A)
75 -
50 ----------------------------
Red
(B)
----------25 -
1
50
100
Log Dose (mg)
Which drug has more potency? And why?
Dose-Response Functions, contd.
Biological Effect
Efficacy & Potency
A
B
Which drug has more efficacy? Which drug has more potency? And
why?
Efficacy: A=B
Potency: A>B
Dose-Response Functions, contd.
Biological Effect
Efficacy & Potency
A
B
Which drug has more efficacy? Which drug has more potency? And
why?
Efficacy: A>B
Potency: A=B
Dose-Response Functions, contd.
Biological Effect
Efficacy & Potency
A
B
Which drug has more efficacy? Which drug has more potency? And
why?
Efficacy: A>B
Potency: A>B