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ICPP 2023 > 10 - Pharmacodynamics > Flashcards

10 - Pharmacodynamics Flashcards

1
Q

What determines a drugs action?

A
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2
Q

How do you work out the molarity (concentration)?

A
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3
Q

How do you get from M to mM to um to nm to pm?

A
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4
Q

Why is it important to conside drug concentrations in molarity?

A

Two drugs of the same weight, e.g 100mg, will have a different concentration as they have different molecular weights

1 mole = 6 x 1023 molecules

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5
Q

How do drugs bind to receptor?

A

Reversibly

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6
Q

What does a drug have to have in order to bind to a receptor and cause a response?

A

Affinity + efficacy

(efficacy is intrinsic efficacy and tissue-dependent factors)

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7
Q

Define the following terms:

  • Intrinsic efficacy
  • Efficacy
A
  1. Can cause a conformational change in the receptor to activate it
  2. A measurable response
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8
Q

What are the characteristics of an agonist and antagonist?

A
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9
Q

Why might a drug have affinity and intrinsic efficacy but not cause a response?

A

NO EFFICACY, tissue dependent factors

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10
Q

What is the difference between clinical efficacy and pharmacological efficacy?

A
  • Clinical is how well a treatment succeeds in it’s aim.
  • Pharmacology a drug could have no efficacy, as an antagonist, but could still have clinical efficacy because it treats a disease
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11
Q

How do you measure the binding of ligands to receptors?

A

Incubate radioligands and receptors. Separate bound and free ligands by filtration

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12
Q

Draw a concentration-binding curve with labels?

A

Remember on logs, -11 is smaller than -7

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13
Q

Draw a concentration-response curve with labels.

A
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14
Q

Define the following terms:

  • Kd
  • Emax
  • Bmax
  • EC50
A

- Kd = the concentration of ligand that occupies 50% of receptors. reciprocal measure of affinity

- Emax = Maximum response

- Bmax = Maximum binding capacity

- EC50 = Concentration of ligand that causes 50% of the maximal response. Reciprocal measure of potency,

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15
Q

If a drug has a high potency what does this mean?

A
  • Has high affinity, has low EC50 therefore a high intrinsic efficacy, and cell/tissue-specific components
  • Higher potency = lower dose
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16
Q

What is the difference between concentration and dose of a drug?

A

Concentration = concentration of ligand/drug at receptor is known

Dose = concentration of ligand/drug at receptor is unknown

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17
Q

What is asthma treatment an example of?

A
  • Functional antagonism
  • Selective not specific
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18
Q

What are the two main drugs for asthma treatment and how do they work?

A
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19
Q

What can be a tissue-dependent factor that affects efficacy?

A

Number of receptors on cell

20
Q

How do you measure affinity and potency?

A

Affinity = Kd

Potency = EC50

21
Q

What does a response binding curve graph look like for a 100% binding and no spare receptors?

A
22
Q

Why might there be 100% response at less than 100% binding?

A

Spare receptors

23
Q

Why do spare receptors exist?

A
  • Usually in catalytic receptors, e.g tyrosine kinase
  • Increase sensitivity of cells
  • Lower concentration of ligand needed for same response with more receptors

1. Amplification of signal so not all receptors have to be stimulated

2. Response limited by post-receptor event

24
Q

What is an example of receptors that dont have 100% binding occupancy but full response?

A

M3 receptors, 10% occupancy for maximum contraction

25
Q

What is the relationship between receptors and ligands?

A

When number of receptors increase, potency of drug increases

26
Q

Why do receptor numbers change?

A

- Upregulation: More receptors due to low activity

- Downregulation: Less receptors due to overstimulation (taking drugs)

Downregulation leads to tolerance and withdrawal symptoms

27
Q

What does the graph of a partial agonist look like?

A
28
Q
A
29
Q

What is a measure of intrinsic activity?

A
  • Maximal response, higher response higher intrinsic activity
  • Partial agonists have lower intrinsic activity therefore lower efficacy
30
Q

What is the relevance of partial agonists?

A
  • More controlled responses
  • Act as antagonists when high levels of full agonist
  • Work in absence of ligand
31
Q

Why does heroin cause death?

A

Respiratory depression

32
Q

What is the advantage of using buprenorphine over morphine?

A
33
Q

Why is buprrenorphine used to wean heroin addicts?

A
  • Mixed antagonist
  • Will bind to receptors over heroin, cause some euphoria but not give full effect as partial agonist so withdrawal symptoms
34
Q

What are the three types of antagonism in drugs?

A
  • Reversible Competitive
  • Irreversible Competitive
  • Non-competitive antagonism
35
Q

What is potency?

A

Potency = Affinity + Efficacy

36
Q

Why can a partial agonist cause a full response>

A

Spare receptors

37
Q

What do graphs look like for a reversible antagonist?

A

Reversible competitive can be overcome by increasing the concentration of agonist

38
Q

How is opioid-mediated respiratory depression reversed?

A

Naloxone

High affinity, competitive antagonist, will compete with heroin and opiods for receptors

39
Q

What happens with an irreversible competitive antagonist?

A

Irreversible binding

40
Q

What is an example of irreversible competitive antagonism and why is it advantageous?

A

Lower concentration needed than reversible competitive antagonist

41
Q

What is a treatment for thrombosis?

A

Clopidogrel

(Prodrug - irreversible competitive agonist)

42
Q

What is non-competitive antagonist and an example?

A
  • Binds to allosteric site (not orthosteric where ligand binds) and causes a conformational change in the receptor, changing it’s efficacy or affinity
  • Similar to irreversible competitive antagonist
  • Maraviroc (negative allosteric modulator of chemokine receptor 5 where HIV enters cells)
43
Q

What type of drug molecule are each of these and label them in order of their efficacy and potency

A
44
Q

How does irreversible competitive antagonism work?

A

Covalent bonding of the antagonist to the receptors orthosteric site

45
Q

Why might there be 100% maximum response but only 40% binding?

A

Signal amplification and Spare receptors

ICPP 2023 (31 decks)

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