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Pharm Block 1 > Antagonism and Dose response relationships and Principles of Therapeutics > Flashcards

Antagonism and Dose response relationships and Principles of Therapeutics Flashcards

Part IIa and IIb

1
Q

inhibit or block the effects of an agonist

A

Antagonists

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2
Q

Type of antagonist that combines with the agonist and thereby disallows interaction with its site of action

A

Chemical

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3
Q

Physiological agonists:

A
  1. Activates an opposing physiological input

2. Could be an agonist

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4
Q

eg. Acetylcholine and norepinephrine are _________ of each other with respect to regulation of heart rate.

A

physiological antagonists

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5
Q

Blocks the effects of the agonist at its site of action (i.e. receptor)

A

Pharmacological

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6
Q

Binds to exactly the same site as the agonist

A

Competitive pharmacological antagonist

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7
Q

EC50’ is

A

the EC50 for the agonist in the presence of a given concentration of antagonist;

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8
Q

K-sub-I is

A

the K-sub-D of the antagonist for the receptor

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9
Q

EC50’ =

A

EC50 (1+ ([antagonist]/ K1))

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10
Q

Binds to exactly the same site as the agonist

A

Competitive pharmacological antagonist

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11
Q

The ability of the agonist to produce a response in the presence of a competitive, equilibrium
antagonist is dependent upon

A

the affinity of the antagonist for the receptor and its concentration

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12
Q

R + D RD–> Effect
+
A –> AR No Effect
The ability of the antagonist to be effective is dependent upon both

A

its concentration and the concentration of agonist that is present

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13
Q

R + D RD–> Effect
+
A –> AR No Effect
All else being equal, the antagonist with highest affinity for the receptor will

A

produce the greatest inhibition

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14
Q

Binds to the agonist binding site in a covalent or very slowly reversing manner

A

Irreversible, competitive antagonist

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15
Q

Once the receptors are bound by this type of antagonist, they cannot be activated by agonist. This reduces the receptor pool

A

Irreversible, competitive antagonist

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16
Q

Irreversible, competitive antagonist :
When we look at the effect of the agonist in the presence of a non-equilibrium antagonist, the EC50 value _________ but the Emax is ________.

A

does not change

reduced

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17
Q

Therapeutic implications of using a non-equilibrium antagonist

(i) New receptor synthesis is ….
(ii) The degree of inhibition produced is not influenced very much by ….

A
  • the only way to overcome the effects of the antagonist

- the concentration of agonist present

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18
Q

a) Blocks the activation of the receptor by an agonist at a site other than the agonist binding site;

A

Noncompetitive pharmacological antagonist

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19
Q

blocks the signal transduction step

A

Noncompetitive pharmacological antagonist

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20
Q

D + R DR –X–> Effect

A

Noncompetitive pharmacological antagonist

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21
Q

Noncompetitive pharmacological antagonist:

The agonist concentration curves look steeper/same as the effect of an irreversible, competitive antagonist

A

Same

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22
Q

Noncompetitive pharmacological antagonist:
Emax is _________ for non-competitive inhibitor
EC50 does/does not change
Is/is not influenced by presence of spare receptors

A

reduced
does not
is not

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23
Q

Noncompetitive pharmacological antagonist:

Antagonist effect is dependent or independent of agonist concentration at the receptor

A

independent

24
Q

Noncompetitive pharmacological antagonist:

Can be used to inhibit the effects of multiple agonists that use

A

the same signal transduction cascade (eg. inhibition of voltage operated calcium channels)

25
Q

Partial agonist/partial antagonist (PA)

1. Ligands that have affinity for the receptor and an intrinsic activity between

A

1 and 0

26
Q

When a partial agonist is present alone, one sees an

A

agonist effect

27
Q

when a partial agonist is present in combination with a full agonist, one sees an

A

antagonist-like effect

28
Q

receptors are in equilibrium between

A

actively signaling (Ra) and inactive (Ri) forms

29
Q

An agonist shifts the equilibrium of Ra and Ri relationship towards

A

more receptors in the Ra form

30
Q

__________ has no effect, and therefore does not affect this equilibrium at all

A

A true antagonist

31
Q

There is a class of ligand that has been identified that can shift the equilibrium toward the Ri form – called

A

“inverse agonists”

32
Q

Inverse agonists ___________tonic activity of the receptor

A

decrease

33
Q

A fundamental of therapeutics is that a relationship exists between the dose of a drug administered and its therapeutic effect

A

The dose response relationship

34
Q

Idealized dose response curves mirror the concentration-effect curves one obtains in the laboratory

A

The dose response relationship

35
Q

Factors that can intervene between the site of drug administration and its ultimate site of action; include:

A

(1) Absorption
(2) Distribution
(3) Metabolism and excretion

36
Q

______ is the relationship between the amount of drug administered and its effect

A

Potency

37
Q

ED50 value is inversely/directly related to potency

A

Inversely

38
Q

Potency determines the position of the curve on the

A

x-axis

39
Q

Determinants of potency

A

(1) affinity for the site of action
(2) ability to reach the site of action
(3) Both are important as is shown in the beta blocker example

40
Q

_________is the maximal effect that is produced by a drug

A

Efficacy

41
Q

On the graph, Efficacy is the maximum point on the _______ that is reached

A

y-axis

42
Q

Determinants of efficacy include:

A
  • Intrinsic activity
  • characteristics of the effector
  • limitations on the amount of drug that can be administered (often due to adverse effects)
43
Q

Deviations from this shape (sigmoid)can occur because of:

A

(1) Additive effects of the drug
(2) Threshold effects
(3) Antagonist effects

44
Q

Due to _____________ rarely is a physician able to determine a dose-response curve in an individual patient

A

Biological variability among patients

45
Q

Most drug effects follow a _________

More often depicted as a ____________distribution

A

log-normal distribution

cumulative frequency

46
Q

Reasons for variations in responses among individuals

A

Pharmacokinetic differences
Variations in the amount of endogenous agonist present
Changes in the number or functioning of the drug target
Differences in a component distal to the drug target

47
Q

unexpected based upon the mechanism of action of the drug

A

idiosyncratic drug responses

48
Q

at the tails of the frequency distribution

A

hyporeactive or hyperreactive

49
Q

allergic or inflammatory response to the drug

A

hypersensitivity

50
Q

slowly developing resistance to the drug

A

tolerance

51
Q

rapidly developing resistance to the drug

A

tachyphylaxis

52
Q

Cumulative frequency relationships between drug dose and population response are called

A

quantal dose response curves

53
Q

Y or X-axis is a quantal measure of the response or effect

(1) i.e. it is an all or none measure

A

Y

54
Q

the ratio of TD50/ED50

A

Therapeutic index

55
Q

Shape of the curve reflects

A

the variability in response in the

population

56
Q

These three things are all obtained depending upon the response measured

A

ED50, TD50, LD50

Pharm Block 1 (23 decks)

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