Basic pharmacology Flashcards
1
Q
What are signs of receptor action?
A
- Dose responsivness to ligand
- Saturability of effect
- Reversibility of effect
2
Q
Define efficacy (in a ligand)
A
Ability of a ligand to produce effect (full agonist has efficacy of 1)
3
Q
Explain pharmacological efficacy.
A
- Receptors have two conformations in equilibrium, active and inactive
- If ligand alters equilibrium of receptor conformations, it is an agonist. (most drugs are antagonistic or partial agonists)
- If ligand makes a submaximal change in equilibrium, it is a partial agonist
4
Q
Define potency.
A
A dose required for a specific effect (focus on receptor or outcome, identification of target levels is crutial)
“If you need a low dose and have a high effect fast, then you have a potent drug”
5
Q
Define competitive antagonist.
A
- Binds to the same site as agonist
- If bound, prevents agonist binding
- Excess agonist will compete off antagonist, if antagonist binds reversibly
6
Q
Define non-competitive antagonist .
A
- Don’t share binding site with agonist
- Cannot be competed away by agonist
- Prevent effect upon agonist binding
- Reduce agonist Emax rather than potency
- Effect on agonist dose curve like irreversible antagonist
7
Q
Desensitisation and tachyphylaxis
A
- Change in receptor (ex. phosphorylation),
- loss of receptor (internalization),
- exhaustion of mediator,
- increased metabolic degradation of the drug,
- physiological adaptation,
- active extrusion of drugs from cells.
8
Q
Explain constitutively active receptors.
A
- In rest state they are largely active
- With ligand are they mostly inactive (Ligands causing shift to inactive receptor are called inverse agonists)
9
Q
What happens when a competitive agonist binds irreversible?
A
- agonist cannot compete it away from the receptor
- the dose-response curve will not only be shifted to the right
- the maximal effect produced by the agonist will also be limited
