Pharmacodynamics Flashcards
(39 cards)
Define what the term ‘ Pharmacodynamics ‘ means
The study of interaction of drugs on biological systems
Define what a drug is ?
A chemical substance which interacts with a receptor to produce a physiological response .
How does a drug produce a effect?
needs to be initially detected does this by Binding to target - common drug protein targets are
Receptors
Enzymes
Transporters
Ion channels
Both allow molecules to move across cell membrane
Name a drug that can bind to a transporter ( Carrier molecule )
Tricyclics antidepressant
Name a drug that can bind with the ion channels
Nimodopine
What is a receptor ?
A region of a tissue or molecule in a cell membrane which responds specifically to a particular neurotransmitter , hormone , antigen or other substance
Ultimately are proteins interacting with extra cellular physiological signals and converting them into intracellular effects .
If nothing is bound to a receptor what are they termed as ?
Functionally silent
Where can receptor proteins be found ?
Can be found on the cell membrane or within constituents of the cell such as nucleas or cytoplasm
Where can the enzyme protein be found ?
Inside or outside the cell
What is a ‘ligand “?
A ligand is a molecule which will fit into the active site of the receptor essentially turning it on
What happens when the ligand binds to the ligand binding site ?
When it binds to the binding site if the receptor proteins , the receptor will under a ‘ conformational change ‘. This change alters the proteins function
The usefulness of a drug depends on …
Its ability to act on a particular receptor.
Drug must show high degree of binding site specificity
Drugs have certain specificity . True or False
Explain why
False .
No drug has certain specificity , many drugs will produce side effects because they will interact with a number of receptors
Explain the two way process of drug specificity .
Certain classes drugs will bind to certain receptors
Certain receptors recognise certain ligands
What is an agonist ?
An agonist is a drug that is able to bind to a receptor to mimic the action of a hormone , or of a transmitter and hence induce a cullular /physiological response
Can be a full or partial response
Agonist possess two qualities , what are they ?
Affinity - they are able to bind successfully to the receptor
Efficacy - are able to generate a response as a result of the binding
Explain the concept of occupancy .
When a drug and receptor combine to form a reversible complex ( not permanent- drug will leave )
Drug + receptor = drug receptor complex = responses
What does the simple occupancy theory suggest ?
The intensity of a response of a drug is proportional to the number of receptors that the drug occupies
Max response - when all avail receptor are occupied
Name and explain a interaction that is not explained by the simple occupancy theory ?
An agonist may achieve max response when only fraction of total number of receptors are occupied
Suggest there is some receptor reserve eg. Acetylcholine
Use the whiteboard to draw a graph explaining the SOT
When high doses are reached , the receptors achieve saturation , curve flattens
Any further increase of dose will not have affect on the occupancy as all available receptors are occupied by drug
What is the term used to describe a drug and receptor coming together and breaking away ?
Association and disassociation
Equilibrium …
The rate of reaction of drug and receptor molecules coming oath there is equal to the rate of reactions where drug and receptors are breaking apart
Use the whiteboard to draw a graph showing the equilibrium association constant
We can identify the conc of drug required to occupy 50% of receptor sites at equilibrium
Ka- equilibrium association constant
How would you determine the affinity of a drug ?
Take reciprocal of Ka
1/Ka= Kd
Kd - equilibrium disassociation constant
Drug and receptor breaking apart
