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Cell Physiology And Pharmacology > Pharmacodynamics: Drugs and Drug Targets > Flashcards

Pharmacodynamics: Drugs and Drug Targets Flashcards

1
Q

What type of proteins are the main drug targets?

A

GPCRs

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2
Q

What is critical in determining drug action?

A

Concentration of drug molecules around receptors

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3
Q

What is the equation of molarity?

A

Molarity (M) = g/L / molecular weight

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4
Q

What is drug binding governed by?

A

Association and dissociation

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5
Q

Which law is related to concentrations of reactants and products?

A

Law of mass action

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6
Q

What is the difference between an agonist and an antagonist?

A

Agonist - Activates a receptor

Antagonist - Blocks the binding of an endogenous agonist

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7
Q

Describe the term ‘affinity’

A
  • How well a drug molecule interacts with a receptor

Higher Affinity = Stronger Binding

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8
Q

What is intrinsic efficacy?

A

Degree to which a ligand enables a receptor to adopt a fully or partially activated state

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9
Q

What is efficacy?

A

Ability of a ligand to cause a response

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10
Q

What do agonists have that antagonists don’t?

A

Efficacy

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11
Q

How can binding of ligand to receptors be measured?

A

Using radioactive labelling of ligand

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12
Q

What is Bmax and what does it indicate?

A
  • Maximum binding capacity

- Informs about the number of receptors

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13
Q

What is Kd?

A
  • Dissociation constant showing ligand affinity

- Ligand concentration at which 50% of receptors are occupied

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14
Q

How are Kd and affinity related?

A

Low Kd = High affinity

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15
Q

What is Emax?

A
  • The maximal response of the system to a ligand binding

- 100% of the measured response

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16
Q

Which curve represents Emax?

A

Concentration-Response curve

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17
Q

What is EC50 a measure of and what is it dependent on?

A
  • Potency

- Dependent on affinity and intrinsic efficacy

18
Q

How is EC50 determined?

A

Concentration of the ligand required to cause 50% of its own maximal response

19
Q

Do all receptors have to be occupied to reach a maximum response?

A

No there can be spare receptors

20
Q

What other factor can limit response other than the number of receptors?

A

Post-receptor response

E.g. a muscle has a limit to its contraction

21
Q

What do spare receptors increase?

A

Sensitivity

22
Q

Why do spare receptors exist?

A

Due to amplification in the signal transduction pathway

23
Q

What can change the number of receptors?

A
  • External influences (drugs)

- Physiological/pathological circumstances

24
Q

What stimulus do receptor numbers increase and decrease in response to?

A
  • Increase in response to low activity

- Decrease in response to high activity

25
Q

Name 2 differences between full and partial agonists

A

Full - high efficacy and intrinsic activity
- high Emax
Partial - low efficacy and intrinsic activity
- low Emax

26
Q

What is a partial agonist?

A

A substance which cannot produce maximal effect even with full receptor occupancy

27
Q

Why are partial agonists commonly used as drugs?

A
  • Allow a more controlled response
  • Work in absence of endogenous ligand
  • Can act as an antagonists
28
Q

What is a clinical example of a partial agonist as a drug?

A

buprenorphine use instead of heroin

29
Q

What are the effect of partial agonists dependent on?

A
  • Compound

- Target cell/tissue

30
Q

What are the 3 methods of action that antagonists have as drugs?

A
  • Reversible competitive antagonism
  • Irreversible competitive antagonism
  • Non-Competitive Antagonism
31
Q

What is reversible competitive antagonism dependent on?

A
  • Concentration of agonist and antagonist

- Dynamic equilibrium between ligands and receptors

32
Q

How can reversible competitive antagonism be overcome?

A

By adding more agonist

33
Q

What is IC50?

A

Concentration of antagonist giving 50% inhibition

34
Q

Give an example of reversible competitive antagonism

A

Effect of naloxone on mew-opioid receptors

35
Q

What is the result of irreversible competitive antagonism?

A

Causes depression of the maximal response

36
Q

Give an example of irreversible competitive antagonism

A

Treatment of thrombosis with clopidogrel

37
Q

Which 2 sites are utilised in non-competitive antagonism?

A
  • Orthosteric

- Allosteric

38
Q

What can allosteric antagonists influence?

A
  • Effect of the orthosteric ligand

- Binding at the orthosteric site

39
Q

What effect does non-competitive antagonism on receptor subtype selectivity?

A

Increases

40
Q

Give an example of non-competitive antagonism

A
  • Maraviroc in HIV

- Prevents HIV entering the cell

Cell Physiology And Pharmacology (17 decks)

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