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BIOL2048 - Principles of Pharmacology > Pharmacodynamics > Flashcards

Pharmacodynamics Flashcards

1
Q

What does is pharmacodynamics the study of?

A

Drug-receptor interactions and their biological response

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2
Q

What are the general properties of receptors?

A

Low concentration, high affinity, selective, reversible reaction, complementary binding site

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3
Q

How is the affinity of a drug for its receptor quantified?

A

Equilibrium dissociation constant Kd

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4
Q

What unit is Kd measured in?

A

M

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5
Q

Which out of antagonists and agonists cause a conformational change in the receptor?

A

Agonists

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6
Q

What is the law of mass action?

A

D + R <–> DR

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7
Q

How is the rate of forward reaction mesured?

A

k1 [D][R]

1 as subscript

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8
Q

ow is the rate of backward reaction measured?

A

K-1 [DR]

-1 as subscript

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9
Q

What is Kd at equilibrium?

A

[D][R] / [DR]

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10
Q

What is the Langmuir equation?

A

r = [D] / [D]+Kd

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11
Q

What is represented by r in the Langmuir equation?

A

Fractional occupancy of receptors

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12
Q

What shape will the curve of r against [D] be?

A

Rectangular hyperbola

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13
Q

What shape will the curve of r against log [D] be?

A

Sigmoidal, approximately linear between 20-80% fractional occupancy

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14
Q

In what situation is [D] equal to Kd?

A

When r (fractional occupancy) = 1/2

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15
Q

For what interactions can the Langmuir equation / r-log[D] plots be used?

A

Simple bimolecular interactions

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16
Q

How can the Langmuir equation be modified to account for complex interactions?

A

r = [D]n / [D]n + Kd

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17
Q

How can the Hill coefficient n be found?

A

Gradient of log r/1-r against log[D]

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18
Q

What does a Hill coefficient of > 1 represent?

A

Positive cooperativity

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19
Q

What does a Hill coefficient of < 1 represent?

A

Negative cooperativity

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20
Q

What does a Hill coefficient of 1 represent?

A

Simple interaction

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21
Q

What is the occupancy theory?

A

Response [E] is directly proportional to number of receptors occupied

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22
Q

What is the rate theory?

A

Response [E] is directly proportional to rate of receptor occupation

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23
Q

What does R equal in occupancy theory?

A

E / Emax and D / D + Kd

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24
Q

What is R in occupancy theory?

A

Fractional response

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25
Q

What is pD2?

A

-log of [D] that gives 1/2 maximal response, always positive

26
Q

At half maximal response, what can be said about [D]?

A

It is equal to Kd

27
Q

What is quantified by pD2?

A

Affinity of agonist for its receptor

28
Q

What does a high pD2 indicate?

A

Drug acts at low concentrations

29
Q

What is competitive antagonism?

A

Agonist and antagonist bind to the same site

30
Q

How can competitive antagonists be overcome?

A

Increasing drug concentration

31
Q

What is non-competitive antagonism?

A

Antagonist binds to different site to agonist, or acts irreversibly

32
Q

What is a common example of competitive antagonism?

A

Acetylcholine (agonist) against atropine (antagonist)

33
Q

What happens to an E/Emax against log[D] curve when more competitive antagonist is added?

A

Shifts in parallel to the right

34
Q

What happens to an E/Emax against log[D] curve when more non-competitive antagonist is added?

A

Flattens downwards

35
Q

Which type of antagonism decreases Emax?

A

Non-competitive

36
Q

What is Ka[D] / (KdKa + Kd[A] + Ka[D])?

A

[DR] / Rt (total receptors)

37
Q

What is the dose ratio?

A

Ratio of agonist concentration that elicits the same response in absence or presence of antagonist

38
Q

What is the simplified Gaddum-Schild equation?

A

[A] / Ka = [Da]/[D0] - 1

39
Q

How is dose ratio calculated?

A

[Da] / [D0]

40
Q

What is pA2?

A

-log of antagonist concentration that gives dose ratio of 2

41
Q

How can pA2 be calculated?

A

-log[Ka]

42
Q

What is pAx?

A

-log of antagonist concentration that gives dose ratio of x

43
Q

What is specificity assumption of the occupancy theory (assumption 1)?

A

There are specific receptors for specific agonists

44
Q

What is the response assumption of the occupancy theory (assumption 2)?

A

All agonists for a given receptor can produce the same maximal response

45
Q

What is the reversibility assumption of the occupancy theory (assumption 3)?

A

The drug-receptor interaction is rapidly reversible

46
Q

What is the accessibility assumption of the occupancy theory (assumption 4)?

A

All receptors are equally accessible to the drug

47
Q

What is the interaction assumption of the occupancy theory (assumption 5)?

A

The receptors do not interact with each other

48
Q

What is the occupation assumption of the occupancy theory (assumption 6)?

A

The maximum response occurs when all receptors are occupied

49
Q

What is the phenomenon of partial agonists?

A

Some agonists produce only a weak response

50
Q

How can a partial agonists interact with a full agonist?

A

Acting as a competitive antagonist

51
Q

What is intrinsic activity (alpha) a measure of?

A

Ability for a drug to produce an effect

52
Q

What is the intrinsic activity of a full agonist?

A

1

53
Q

What is the intrinsic activity of a partial agonist?

A

< 1

54
Q

What is the intrinsic activity of an antagonist?

A

0

55
Q

What is the phenomenon of spare receptors?

A

Maximum response can be reached without every receptor being occupied

56
Q

At low concentrations, what does a high efficacy antagonist appear to be?

A

Competitive

57
Q

At high concentrations, what does a high efficacy antagonist appear to be?

A

Non-competitive

58
Q

What modifications are made to the occupancy theory to account for partial agonists and spare receptors?

A

The effect will depend on the affinity of the drug for receptor, and the ability of the drug to induce a conformational change

59
Q

What is stabilised by a high efficacy agonists?

A

Active receptor conformation

60
Q

What is meant by a receptor’s constitutive activity?

A

Basal activity in resting state

61
Q

What do inverse agonists do?

A

Decrease constitutive activity of a receptor

BIOL2048 - Principles of Pharmacology (1 decks)

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