Pharmodynamics Topic Review Flashcards
1
Q
Define ligand
A
- a substance that can interact with a targe protein or REcepetor - usually bind to a specific site on the signalling protein.
2
Q
Define agonist
A
- a substance that has affinity and binds to a recepetor and activates the receptor to then produce a measurable response
3
Q
Define antagonist
A
Ligand that have affinity for a receptor or target protein but do not produce a biological response
- they block the effects of agonists
4
Q
Define affinity
A
- measure of strength between a ligand/drug to a receptor
-
5
Q
What is the Measurement used to define affinity ?
A
Affinity is measured by Kd.
- the lower the Kd , the greater the affinity
6
Q
Define Kd
A
Concentration of ligand at which 50% of all available receptors bound.
7
Q
Define intrinsic efficacy
A
- the ability of a ligand to generate an activate form of the receptor - often a conformation change. This is exhibited by agonists only.
8
Q
Define ligand efficacy
A
Ability for ligand to cause a measurable biological response
9
Q
Define agonist potency’
A
- potency is described as the the concentration of a drug that evokes 50% of its maximal response (Emax)
- EC50 is used to represent this concentration
- the lower the value of EC50 the more potent the drug/ ligand is because a lower concentration of drug/ligand is required to generate 50% of maximal response
10
Q
Define partial agonist
A
- Ligands that evoke responses that are lower than the maximal response of a full agonist
- they have a lower Emax value
11
Q
Compared to a full agonist , a partial agonist has …
A
Lower intrinsic efficacy
12
Q
Define Bmax
A
Found on the binding curve
- concentration of available receptors in sample tissue
- make sure it doesn’t touch the line
13
Q
Should Emax touch the line ?
A
No
14
Q
The EC50 for ACH is 10-7M compared to a kd of 10-6M. What pharmacodynamic principle explains this difference ?
A
Spare muscarnic M3 receptors
