Pharmacodynamics

Question 1

Define what the term ‘ Pharmacodynamics ‘ means

Answer 1

The study of interaction of drugs on biological systems

Question 2

Define what a drug is ?

Answer 2

A chemical substance which interacts with a receptor to produce a physiological response .

Question 3

How does a drug produce a effect?

Answer 3

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

Question 4

Name a drug that can bind to a transporter ( Carrier molecule )

Answer 4

Tricyclics antidepressant

Question 5

Name a drug that can bind with the ion channels

Answer 5

Nimodopine

Question 6

What is a receptor ?

Answer 6

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 .

Question 7

If nothing is bound to a receptor what are they termed as ?

Answer 7

Functionally silent

Question 8

Where can receptor proteins be found ?

Answer 8

Can be found on the cell membrane or within constituents of the cell such as nucleas or cytoplasm

Question 9

Where can the enzyme protein be found ?

Answer 9

Inside or outside the cell

Question 10

What is a ‘ligand “?

Answer 10

A ligand is a molecule which will fit into the active site of the receptor essentially turning it on

Question 11

What happens when the ligand binds to the ligand binding site ?

Answer 11

When it binds to the binding site if the receptor proteins , the receptor will under a ‘ conformational change ‘. This change alters the proteins function

Question 12

The usefulness of a drug depends on …

Answer 12

Its ability to act on a particular receptor.

Drug must show high degree of binding site specificity

Question 13

Drugs have certain specificity . True or False

Explain why

Answer 13

False .
No drug has certain specificity , many drugs will produce side effects because they will interact with a number of receptors

Question 14

Explain the two way process of drug specificity .

Answer 14

Certain classes drugs will bind to certain receptors

Certain receptors recognise certain ligands

Question 15

What is an agonist ?

Answer 15

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

Question 16

Agonist possess two qualities , what are they ?

Answer 16

Affinity - they are able to bind successfully to the receptor
Efficacy - are able to generate a response as a result of the binding

Question 17

Explain the concept of occupancy .

Answer 17

When a drug and receptor combine to form a reversible complex ( not permanent- drug will leave )

Drug + receptor = drug receptor complex = responses

Question 18

What does the simple occupancy theory suggest ?

Answer 18

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

Question 19

Name and explain a interaction that is not explained by the simple occupancy theory ?

Answer 19

An agonist may achieve max response when only fraction of total number of receptors are occupied
Suggest there is some receptor reserve eg. Acetylcholine

Question 20

Use the whiteboard to draw a graph explaining the SOT

Answer 20

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

Question 21

What is the term used to describe a drug and receptor coming together and breaking away ?

Answer 21

Association and disassociation

Question 22

Equilibrium …

Answer 22

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

Question 23

Use the whiteboard to draw a graph showing the equilibrium association constant

Answer 23

We can identify the conc of drug required to occupy 50% of receptor sites at equilibrium

Ka- equilibrium association constant

Question 24

How would you determine the affinity of a drug ?

Answer 24

Take reciprocal of Ka
1/Ka= Kd
Kd - equilibrium disassociation constant
Drug and receptor breaking apart

Question 25

What does affinity mean ?

Answer 25

This is the strength of the binding between the drug and receptor
Drug with high affinity will disassociate at a slower rate , drugs will low affinity will break away rapidly
Characterised by the equilibrium disassociation constant

Question 26

What does efficacy mean ?

Answer 26

Used to be referred to as intrinsic activity
Ability of drug to elicit response once bound to a receptor
The max effect the drug is capable of

Question 27

What is a dose response curve ?

Answer 27

Graph which tracks the response to various concentrations or doses of a drug

Question 28

Sate how two different type of graphs can plot the same information

Answer 28

Linear scale - equal jumps on x axis

Log scale - unequal jumps between doses

Question 29

Name two different types of dose response curves

Answer 29

Graded - effects in an individual on a physiological response such as heart rates
Quantal - data in no of individuals trying to work out if drug is effective or not as dose varies

Question 30

What is a partial agonist ?

Answer 30

An agonist that cannot elicit the max same response as a full agonist
Have reduced efficacy

Question 31

Explain the two theories in why an agonist is partial ?

Answer 31

1) PA binds fine but is less able to change structure when binding is done - less efficient at initiating the transduction pathway
2)Receptor site is constantly changing from active and inactive
If drug binds to inactive state no response

Question 32

What is potency?

Answer 32

Linked with affinity , number of receptors and efficacy

The dose required to produce a specific intensity of response

ED50 can be good indicator of potency

Question 33

What is ED50?

Answer 33

Effective dose

Dose that produces an effective therapeutic response in 50% of people taking the drug

Question 34

What is the TD50?

Answer 34

Dose which causes toxicity in 50% of people taking the drug

Animals

Question 35

What is LD50?

Answer 35

Dose that causes death in 50% of people given the drug
Lethal dose
Animals

Question 36

Plot therapeutic and toxic effects of a drug ?

Answer 36

Ideally should be wide margin between the two
Therapeutic index (TI) = TD50/ED50
Safe drug will have higher therapeutic index

Question 37

What is an antagonist ?

Answer 37

Drugs that may compete with natural agonist for receptor but don’t induce a response alone - this is called a competitive antagonist
They have affinity but no efficacy

Effectively dilutes receptor concentration

Question 38

What is an irreversible antagonist ?

Answer 38

Drugs may bind strongly and permanently to the Receptor and prevent access of natural against
Will deactivate receptor and will be out of action for a period which depends on rate of synthesis for that type of receptor

Question 39

What is an non competitive antagonist ?

Answer 39

Binds to irreversibly to same site of agonist or bind to different site

Reduction in max effect produced

Cannot be reversed by increasing agonist concentration