Introduction to Drug Action

Question 1

What is pharmacodynamics?

Answer 1

What a drug does to the body - the biological effects and the mechanism of action

Question 2

What are pharmacokinetics?

Answer 2

What the body does to a drug - absorption, distribution, metabolism and excretion of drugs and their metabolites

Question 3

What must a drug act with a degree of in order to be useful as a therapeutic agent?

Answer 3

Selectivity

Question 4

What is selectivity?

Answer 4

The ability of a drug to distinguish between different molecular targets within the body

Question 5

What does the acronym ADME stand for and what is it involved in?

Answer 5

Absorption
Distribution
Metabolism
Excretion of drugs and their metabolites

Pharmacokinetics

Question 6

What is the narrow definition of a drug?

Answer 6

Any single substance of known structure sed in the treatment, prevention of diagnosis of disease

Question 7

In what way are penicillins selective?

Answer 7

They inhibit an enzyme responsible for cell wall synthesis in bacteria but as animal cells don’t have a cell wall human cells are not affected

Question 8

What regulatory proteins do many drugs bind to in order to cause an action?

Answer 8

Enzymes
Carrier molecules
ion channels
Receptors

Question 9

What additional targets (aside from proteins) do drugs bind to in order to cause an action?

Answer 9

RNA

DNA

Question 10

What are receptors?

Answer 10

Protein macromolecules on or within cells that mediate the biological action of hormones

Question 11

What are the two types of drugs acting on receptors?

Answer 11

Agonists

Antagonists

Question 12

What his an agonist?

Answer 12

A drug that binds to a receptor to produce a cellular response

Question 13

What is an antagonist?

Answer 13

A drug that reduces or blocks the actions of an agonist by binding to the same receptor

Question 14

What do K+1 and K-1 represent in the agonist equation?

Answer 14

K+1 - rate of agonist bindings

K-1 - affinity and efficacy

Question 15

What is the equation for agonists?

Answer 15

A+R (K+1/K-1) AR (beta/alpha) AR*

Question 16

What is the process of an agonist binding to a receptor?

Answer 16

The agonist binds to the receptor, forming an agonist-receptor complex.
This causes a conformational change, leading to a response.
This is reversible

Question 17

What is the process of going from agonist and receptor to an agonist-receptor complex called?

Answer 17

Binding step

affinity

Question 18

What is the process of the agonist-receptor complex changing confirmation and producing a response called?

Answer 18

Activation step

efficacy

Question 19

What do beta and alpha represent in the agonist equation?

Answer 19

Beta - rate of receptor activation

Alpha - rate of receptor deactivation

Question 20

Do agonists possess affinity or efficacy?

Answer 20

Yes, both

Question 21

What represents affinity?

Answer 21

K+1/K-1

Question 22

What represents efficacy?

Answer 22

Beta/alpha

Question 23

What is affinity?

Answer 23

The strength of association between a ligand and receptor

Question 24

At low affinity, what is the position of equilibrium and the dissociation rate for the binding step?

Answer 24

To the left (reactants)

Fast dissociation rate

Question 25

At medium affinity, what is the position of equilibrium and the dissociation rate for the binding step?

Answer 25

In the middle | Moderate dissociation rate

Question 26

At high affinity, what is the position of equilibrium and the dissociation rate for the binding step?

Answer 26

To the right (products) | Slow dissociation rate

Question 27

What is affinity defined by?

Answer 27

Chemical bonds between a ligand and its receptor

Question 28

What is efficacy?

Answer 28

The ability of an agonist to evoke a cellular response

Question 29

At low affinity, what is the position of equilibrium for the activation step?

Answer 29

To the left - reactants

Question 30

At high affinity, what is the position of equilibrium for the activation step?

Answer 30

To the right - products

Question 31

What is an antagonist?

Answer 31

A drug that reduces or blacks the actions of an agonist by binding to the same receptor

Question 32

How many steps are involved in agonists?

Answer 32

Two

Question 33

How many steps are involved in antagonists?

Answer 33

One

Question 34

What is the step for antagonists c called?

Answer 34

Binding step

Question 35

Do antagonists possess affinity or efficacy

Answer 35

Only affinity

Question 36

What is the action of antagonists?

Answer 36

Bind to receptors but do not activate them to block receptor activation by antagonists

Question 37

How is the relationship between concentration (or dose) and effect described?

Answer 37

Hyperbolic | steep gradient then decreasing until tapers off

Question 38

What is EC50(/ED50)?

Answer 38

The concentration of agonist that elects a half maximal effect

Question 39

What is AR*?

Answer 39

The activated agonist-receptor complex

Question 40

What does EC50/ED50 stand for?

Answer 40

EC - effected concentration | ED - effected dose

Question 41

Why are linear graphs of concentration against effect converted into logarithmic graphs?

Answer 41

EC50 is easier to tell on a logarithmic lot

Question 42

On a semi-logarithmic plot, how is the relationship between concentration and effect described?

Answer 42

Sigmoidal - s shaped

Question 43

What is potency?

Answer 43

A measure of drug activity expressed in terms of the amount required to produce an effect of given intensity.

Question 44

What is used when comparing drugs on a semi-logarithmic graph?

Answer 44

EC50

Question 45

How can reversible competitive antagonism be overcome?

Answer 45

Increasing the concentration of agonist

Question 46

What is reversible competitive antagonism?

Answer 46

The binding of agonist and antagonist, both of which are reversible, occur at the same (orthosteric) site

Question 47

What is non-competitive antagonism?

Answer 47

An agonist binds to the orthosteric site and antagonist binds to a separate allosteric site and thus this is not competitive Both may occupy receptor at same time but activation cannot occur when antagonist is bound

Question 48

What do competitive antagonists cause to happen to a semi-logarithmic graph?

Answer 48

Parallel rightward shift of agonist response curve but maximum response is unchanged

Question 49

What do non-competitive antagonists cause to happen to a semi-logarithmic graph?

Answer 49

Depress the slope and the maximum of the concentration response curve but no rightwards shift

Question 50

What is the effect of increasing the concentration of a competitive antagonist on a semi-logarithmic graph?

Answer 50

Progressive rightward shift, no depression of slope or maximum response

Question 51

What is the effect of increasing the concentration of a non-competitive antagonist on a semi-logarithmic curve?

Answer 51

Progressive depression of maximum response and slope, but no rightward shift

Question 52

What are partial agonists?

Answer 52

Ones with lower efficacy than full agonists