Session 6: Pharmacodynamics Flashcards
What is a millimolar in standard form? (mM)
10^-3
What is a micromolar in standard form? (Mew M)
10^-6
What is a nanomolar in standard form? (nM)
10^-9
What is a picomolar in standard form? (pM)
10^-12
Most drugs bind reversibly to receptors. What is reversible binding?
Binding governed by association and dissociation.
Define ligand.
A molecule or Ion which binds to a specific receptor.
What is the binding of a ligand to a receptor governed by?
It’s affinity.
Define ligand efficacy.
The ability of a ligand to cause a response.
What is receptor activation governed by?
Intrinsic efficacy of a ligand.
What do agonist ligands have?
- affinity (can bind to the receptor)
- intrinsic efficacy (ability to activate receptor)
- efficacy (ability to cause a response)
What do antagonist ligands have?
- affinity ONLY(can bind to the receptor)
Prevents a response by preventing endogenous ligands from binding.
How can drug-receptor interactions be measured?
Radioligands
What is Kd
Dissociation constant
What is Ec50?
POTENCY: Effective Concentration which gives 50% of the maximal response.
Define concentration in relation to drug administering.
The concentration of drug at the site of action. E.g. receptor in tissues and cells
Define dose in relation to drug administering.
The concentration at the site of action is unknown.
What is the potency sum?
Affinity + Efficacy AND the number of receptors on a cell
When are spare receptors present?
- signal transduction becomes amplified later on
- response limited by post-receptor event I.e. A muscle can only contract so hard
Why are spare receptors present?
To increase sensitivity, I.e. It allows responses at low concentration of agonists
TRUE OR FALSE: receptor numbers are fixed.
False: they tend to increase with low activity to up-regulation and visa versa due to physiological, pathological or drug-induced changes
What is a partial agonist?
A ligand which does elicit a maximal response.
What is usually different about partial agonists?
Usually have lower intrinsic efficacy.
Give 3 reasons why partial agonists are important.
- Allow a more controlled response
- Work in the absence/ low levels of endogenous ligand
- Can act antagonistic if levels of full agonist are high
Give an example of a partial agonist.
Buprenorphine (higher affinity I.e. Lower Kd but lower efficacy than morphine)
TRUE OR FALSE: increaseing the receptor number can change a full against into a partial agonist.
False: other way round silly!
What is IC50?
The concentration of antagonist giving 50% inhibition.
What impact do reversible competitive antagonists have on a concentration-response curve graph?
Shift to the right- think about it, the Kd will increase hence the affinity for the agonist ligand to the receptor will decrease with more molecules of competing ligand present:)
Can you tell I’ve been making these cards for too long now?
