Pharmodynamics I Flashcards

1
Q

What is the difference between biological receptors and binding sites?

A

Biological receptors can bind substances AND initiate a subsequent response while binding sites only bind substances.

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2
Q

What kind of relationship is there between the fractional occupancy of a drug and the dose?

A

Non-linear

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3
Q

What relationship is there between the response and the dose?

A

Non-linear

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4
Q

What does the occupancy fraction depend upon?

A
  • Affinity

- Concentration (of the dose)

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5
Q

Kd

A

Dissociation constant.

It is the concentration of drug required to bind HALF (50%) of the receptors.

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6
Q

What do small Kd values indicate?

A

High affinity for the receptor

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7
Q

ED50

A

Median effective dose.

The dose required to achieve a QUANTAL effect in 50% of the population.

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8
Q

Potency

A

Concentration necessary to produce 50% of a drug’s max response and is expressed as an EC50 or ED50 value

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9
Q

What does the potency of a drug depend on?

A
  • Affinity which is the Kd

- Efficiency of the receptor interaction with the response

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10
Q

What does the clinical effectiveness of a drug depend upon?

A

Emax (maximal efficiency)

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11
Q

EC50

A

Half maximal effective concentration.

Concentration where 50% of its maximal effect is observed (GRADED)

-> Can be quantal, then it is ED50

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12
Q

When does EC50 = Kd?

A

When all spare receptors are bound

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13
Q

How does a competitive antagonist change the DR curve?

A
  • Shifts it right
  • Increases the ED50
  • Emax remains the same
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14
Q

How does a non-competitive antagonist change the DR curve?

A
  • Curve does not shift
  • ED50 remains the same
  • Decrease Emax
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15
Q

What happens to the DR curve with more spare receptors?

A

It gets steeper

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16
Q

How does competition with drugs occur?

A

Dynamic equilibrium is how the competition occurs.

Displacement does NOT occur with drugs on receptor.

17
Q

What is the Fractional Occupancy equation?

A

F.O. = 1/( 1+(Kd/[D]) )

18
Q

What happens to selectivity as drug dose is increased?

A

Selectivity will decrease.

19
Q

The Dose-Response Relationship

A

This is the correspondence between the amount of drug and the magnitude of the effect; increasing the dose, increases the effect in a graded manner.

20
Q

How do Full Agonists affect activity?

A

Efficacy = 100%

21
Q

How do Partial Agonists affect activity?

A

Efficacy = 0 - X - 100%

22
Q

How do Neutral Antagonists affect activity?

A

Efficacy = 0%

23
Q

How do Inverse Antagonists affect activity?

A

0 > Efficacy

24
Q

How do partial agonists affect the DR curve?

A

They compete with the normal agonist (drug) and bring the level of response below one.

“One + a half is less than one and a half”

25
Q

Chemical Antagonism

A

Done via chemical inactivation of a drug

26
Q

Physiologic Antagonism

A

The use of opposing pathways to antagonize the effects of a drug

27
Q

Biologic Antagonism

A

One drug may affect the metabolism or pharmacokinetics of another drug

28
Q

What is the quantal DR curve?

A

The relationship between drug dose and a SPECIFIED effect in a population of individuals

29
Q

TD50

A

The dose required to get 50% of the population reporting this specific toxic effect

30
Q

LD50

A

The dose required to achieve 50% mortality from toxicity

31
Q

What is the therapeutic index?

A

Ratio of the TD50 or LD50 to the ED50

32
Q

What is the therapeutic window?

A

This is the Dosage Range between the minimum effective therapeutic dose and the minimum toxic dose

33
Q

What is the best assessment of drug toxicity?

A

Therapeutic window