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Flashcards in Drug target sites Deck (41):
1

What do drugs do?

Produce specific effects

2

What are the target sites drugs act on?

Receptors

3

What are agonists?

A drug which acts on a receptor and produces a response (increase/decrease activity of the cell)

4

What is an antagonist?

A drug which prevents the response of an agonist

5

What are drug receptor controls?

Selectivity of drug effect
Magnitude (size) of response
Mechanisms to mimic/prevent physiological function

6

What is a dose?

Amount of drug

7

What is concentration?

Amount of drug per unit volume

8

What are the common units of a dose?

Micrograms (ug, 10-6 grams)
Nanomoles (nmoles, 10-9 moles)

9

What are the common units of concentration?

Micromolar (uM, 10-6 moles per litre)
Nanomolar (nM, 10-9 moles per litre)

10

How does an agonist bind to its receptor?

With weak bonds
E.g. electrostatic forces, van der waals bonds and hydrogen bonds

11

What are the reactions between an agonist and receptor to produce an effect?

Agonist + Receptor ←→ Agonist-Receptor
[A] + [R] ←→ [AR]
[AR]→Effect

12

What are drug-receptor interactions?

'Stereo-selective'

13

How are ligand/receptor interactions defined?

In 3 dimensions

14

What does the ligand/receptor interaction mean?

Display selectivity for one stereo-isomer of a ligand over another

15

What is the magnitude of response?

[AR] = [A]
[RT] Kd + [A]

16

What does [A] stand for?

Agonist concentration

17

What does [AR] stand for?

Agonist-receptor concentration

18

What does [Rt] stand for?

Total receptor concentration

19

What does Kd stand for?

Dissociation sonstant

20

What type of response is the magnitude of response?

Hyperbolic

21

What are dose-response curves?

Hyperbolic
Complex relationship between dose and response

22

What are log dose-response curves?

Sigmoid shape
Simple relationship between log dose and response, i.e. log-linear (between 20% and 80% maximum response)

23

What information can be revealed from a log dose-response curve?

Threshold dose
Maximum dose
Effective dose range
Half-maximal effective dose
ED50

24

What is the potency of a log dose-response curve?

Related to affinity of drug for receptor
Determines dose required for effect
ED50 is a useful index of potency

25

What is the efficacy of a log dose-response curve?

An index of maximum response a drug can induce, i.t. its effectiveness

26

What is the efficacy of full agonists?

Have high efficacy (1.0)
Produce the maximum response possible at a given receptor

27

What is the efficacy of partial agonists?

Have low efficacy (<1.0)
Fail to produce the maximum response possible at a given receptor

28

How do antagonists block agonists?

Act on the same receptor site as the agonist
Act at a different site in the pathway leading to a response
Activate an opposing physiological mechanism
Interact chemically with the agonist

29

What are competitive antagonists?

Antagonists which act on the same receptor site as the agonist

30

What do competitive antagonists do?

Have affinity for receptor
Compete with agonist molecules for the receptor

31

Why is there no effect when an antagonist binds to a receptor?

Antagonist has no efficacy at the receptor
The antagonist/receptor complex cannot activate transduction mechanisms and therefore there is no effect

32

What are the two type of competitive antagonists?

Reversible (Surmountable)
Irreversible (Insurmountable)

33

What kind of bonds does a competitive reversible antagonist make with the receptor?

Weak bonds

34

What can happen when agonist concentration is increased when a competitive reversible antagonist is attached to the receptor?

The chance of agonist molecules interacting with the receptor is increased
The effect of the antagonist can be reversed
The antagonist is competitive and reversible

35

In the presence of a competitive reversible antagonist the agonist log-dose response curve changes how?

Is shifted to the right
Is parallel to the curve for the agonist acting alone
Has an unchanged maximum response

36

What happens if the concentration of the agonist increases the reversible competitive antagonist?

The agonist overcomes the effect of the antagonist

37

What kind of bonds does a competitive irreversible antagonist create with the receptor?

Covalent bonds

38

What happens if an antagonist creates covalent bonds with the receptor?

The antagonist binds irreversibly to the receptor
Increasing the concentration of the Agonist cannot reverse the binding of the antagonist
The antagonist is competitive and irreversible

39

In the presence of a competitive irreversible antagonist, what does the log-dose response curve look like?

Is not parallel to the log dose-response curve for the agonist acting alone
Has a depressed maximum response

40

What can happen when agonist concentration is increased when a competitive irreversible antagonist is attached to the receptor?

Does not overcome the depression of the maximum response produced by a competitive irreversible antagonist

41

What kind of agonist log-dose response curve do some competitive irreversible antagonists produce?

Parallel shift before producing a depression in the maximum response