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Medicinal Chemistry > Lecture 5 - Drug Receptor Interactions > Flashcards

Lecture 5 - Drug Receptor Interactions Flashcards

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1
Q

Which amines are chiral?

A

Only quaternary

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2
Q

What are the principles of drug-receptor interactions similar to?

A

Drug-enzyme interactions

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3
Q

Does every receptor have an endogenous ligand?

A

Usually

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4
Q

What is an orphan receptor?

A

A receptor with an unknown endogenous ligand

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5
Q

Compounds with similar ______ will often bind to the same receptor

A

Structure

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6
Q

Do receptors have an infinite binding capacity?

A

No, binding can be saturated

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7
Q

Receptors are ____ specific

A

Tissue (they are in the tissues that need to respond to the ligand)

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8
Q

What does a ligand act as?

A

A chemical signal that produces the biological response at a specific tissue

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9
Q

What type of interactions do drugs use to bind to receptors and which are the most important?

A
  • The same interactions that drugs form with solvents

- Most important - dispersion, H-bonding, ionic, ion-dipole

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10
Q

What are dispersion interaction referred to as for protein interactions?

A

Hydrophobic interactions

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11
Q

Is there a relationship between the number of drug-receptor complexes and the magnitude of biological response?

A

Yes

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12
Q

What is the effect of a drug related to?

A

The fraction of bound receptors

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13
Q

What is Kd and what are its units?

A
  • Equilibrium dissociation constant; the [drug] at which you get half maximal binding
  • mol/L
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14
Q

What is Kd a measure of?

A

How the equilibrium is displaced to free drug and free receptor

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15
Q

What does a small Kd mean?

A
  • More drug-receptor complex, so more biological response

- Tight binding

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16
Q

What is the affinity constant?

A

1/Kd

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17
Q

What does a higher affinity constant mean?

A

Tighter binding

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18
Q

What do we know about a receptor that has a Kd of 1 mM?

A

A 1 mM [drug] will produce half maximal receptor binding

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19
Q

What is [Rt]?

A

Total receptors

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20
Q

What is f?

A

Fraction of receptors bound proportional to biological effect

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21
Q

What is efficacy proportional to?

A

The amount of drug-receptor complexes

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22
Q

What is intrinsic activity?

A

The ability of the drug to produce an effect by forming a drug receptor complex

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23
Q

Are intrinsic activity and affinity related?

A

No

24
Q

Is intrinsic activity dependent on Kd?

A

No

25
Q

When is Emax achieved?

A

When all receptors are bound to drug

26
Q

What is ED50?

A

[drug] at 1/2 Emax

27
Q

Can Kd and ED50 have the same value?

A

Yes, but they are not the same thing

28
Q

What does ED50 reflect?

A

Potency

29
Q

What does a lower ED50 mean?

A

Less drug needed to get the maximal response, therefore more potent

30
Q

Does potency tell you anything about the effect of the drug?

A

No

31
Q

What is potency independent of?

A

Intrinsic activity or efficacy

32
Q

Can a drug have high potency and low intrinsic activity?

A

Yes

33
Q

Often drugs of a similar chemical class that target the same receptor have the same _____ but differ in ______

A
  • Maximal effect

- Potency

34
Q

Why do Kd and ED50 often have the same value?

A

B/c we defined the effect as being directly proportional to receptor binding and we defined maximum effect as being achieved when all receptors are bound

35
Q

Efficacy is the relationship between ____ and _____

A

Effect and amount of drug-receptor complexes

36
Q

What does it mean when Kd > ED50?

A

Maximal effect is achieved without binding all receptors

37
Q

What is spare receptor theory?

A

When maximal effect is achieved without binding all receptors

38
Q

When does spare receptor theory usually happen?

A

When there are a series of biochemical events that transmit the signal of receptor binding across the cell membrane (signal amplification)

39
Q

What do agonists do?

A
  • Bind to receptors
  • Have affinity for the receptor
  • Have intrinsic activity
40
Q

Do most receptors have an endogenous agonist?

A

Yes

41
Q

What is a full agonist?

A

Binds to receptor and is capable of producing the same maximal response as endogenous agonist

42
Q

What is a partial agonist?

A

Can bind to receptor (has affinity) but produces a smaller than maximal response and has a lower intrinsic activity than full agonist

43
Q

What do antagonists do?

A
  • Bind to receptors
  • Have affinity for the receptor
  • Have no intrinsic activity
44
Q

What are the most important antagonists?

A

Competitive and non-competitive

45
Q

What is the difference between competitive and non-competitive antagonists?

A

How they interact with the receptor and an agonist

46
Q

What do competitive antagonists do?

A

Have similar shapes as the agonist and can fit into the agonist binding site

47
Q

Can a competitive antagonist bind to the receptor if the drug is already bound?

A

No

48
Q

What does a competitive antagonist do to Kd?

A

Increases Kd or decreases affinity of agonist

49
Q

How can competitive antagonism be overcome?

A

Increasing the amount of agonist

50
Q

Does a competitive antagonist change the efficacy of the agonist?

A

No, but the apparent ED50 for the agonist increases

51
Q

Why does ED50 change in the presence of a competitive antagonist?

A

Because the antagonist competes with the agonist for the same receptor, which increases the dose needed to achieve the same effect (decreases potency)

52
Q

Do non-competitive antagonists bind to the same site as the agonist and what does this mean?

A

No, so they can be structurally different

53
Q

Does a non-competitive antagonist change the affinity of the agonist for the receptor when it is bound?

A

No

54
Q

What does a non-competitive antagonist do?

A

Binds to or inhibits the empty receptor or the drug-receptor complexes effectively decreasing the pool of receptors

55
Q

A non-competitive antagonist is characterized by _____

A

Decreasing the apparent number of receptors

56
Q

What does a non-competitive antagonist do to Kd and potency?

A

Both remain unchanged

57
Q

Can you overcome non-competitive antagonism by adding more agonist?

A

No

Medicinal Chemistry (14 decks)

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